1. A method of coding video data, the method comprising:coding a first largest coded unit of a slice of video data;identifying, for a current block of video data that is positioned below the first largest coded unit and that neighbors the first largest coded unit and that is included in a second largest coded unit of the slice of video data, one or more blocks from which to determine one or more most probable intra-prediction modes for predicting an intra-prediction mode of the current block of video data based on a location of the one or more blocks, wherein identifying the one or more blocks comprises excluding locations of any block of the first largest coded unit;determining the one or more most probable intra-prediction modes based on respective intra-prediction modes of the identified one or more blocks; and coding data that indicates the intra-prediction mode for the current block based on the one or more most-probable intra-prediction modes.

2. The method of claim 1, wherein the first largest coded unit and the second largest coded unit are included in a single slice of video data.

3. The method of claim 1, wherein identifying the one or more blocks comprises identifying one or more left-neighboring blocks of the block.

4. The method of claim 3, wherein identifying the one or more blocks comprises identifying one or more blocks that are directly adjacent to the block.

5. The method of claim 3, wherein identifying the one or more blocks comprises identifying one or more blocks that are not directly adjacent to the block.

6. The method of claim 1, wherein identifying the one or more blocks comprises identifying a first left-neighboring first block and a second left-neighboring block that is positioned below the block.

7. The method of claim 1, wherein coding the data that indicates the intra-prediction mode for the current block comprises encoding the data block, and wherein the method further comprises:determining residual values for the current block using the intra-prediction mode for the current block; and encoding the residual values and the data that indicates the intra-prediction mode for the current block in an encoded bitstream.

8. The method of claim 1, wherein coding the data that indicates the intra-prediction mode for the current block comprises decoding the data, and wherein the method further comprises:decoding residual values for the current block;intra-predicting the block using the intra-prediction mode for the current block;and combining the intra-predicted residual values with received residual values of the block.

9. An apparatus for coding video data, the apparatus comprising: a memory configured to store video data; and one or more processors configured to:code a first largest coded unit of a slice of the video data; identify, for a current block of video data that is positioned below the first largest coded unit and that neighbors the first largest coded unit and that is included in a second largest coded unit of the slice of video data, one or more blocks from which to determine one or more most probable intra-prediction modes for predicting an intra-prediction mode of the current block of video data based on a location of the one or more blocks, wherein to identify the one or more blocks, the one or more processors exclude locations of any block of the first largest coded unit;determine the one or more most probable intra-prediction modes based on respective intra-prediction modes of the identified one or more blocks; and code data that indicates the intra-prediction mode for the current block based on the one or more most-probable intra-prediction modes

10. The apparatus of claim 9, wherein the first largest coded unit and the second largest coded unit are included in a single slice of video data

11. The apparatus of claim 9, wherein to identify the one or more blocks, the one or more processors are configured to identify one or more left-neighboring blocks of the current block

12. The apparatus of claim 11, wherein to identify the one or more blocks, the one or more processors are configured to identify one or more blocks that are directly adjacent to the current block

13. The apparatus of claim 11, wherein to identify the one or more blocks, the one or more processors are configured to identify one or more blocks that are not directly adjacent to the current block

14. The apparatus of claim 9, wherein to identify the one or more blocks, the one or more processors are configured to identify a first left-neighboring first block and a second left-neighboring block that is positioned below the current block

15. The apparatus of claim 9, wherein the apparatus comprises a video encoder, and wherein to code the data that indicates the intra-prediction mode for the current block, the one or more processors are configured to encode the data, and wherein block the one or more processors are further configured to:determine residual values for the current block using the intra-prediction mode for the current block; and encode the residual values and the data that indicates the intra-prediction mode for the current block in an encoded bitstream.1 6. The apparatus of claim 9, wherein the apparatus comprises a video decoder, wherein to code the data that indicates the intra-prediction mode for the current block, the one or more processors are configured to decode the data, and wherein the one or more processors are further configured to:decode residual values for the current block;intra-predict the block using the intra-prediction mode for the current block;and combine the intra-predicted residual values with received residual values of the block.1 7. A non-transitory computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to:code a first largest coded unit of a slice of video data;identify, for a current block of video data that is positioned below the first largest coded unit and that neighbors the first largest coded unit and that is included in a second largest coded unit of the slice of video data, one or more blocks from which to determine one or more most probable intra-prediction modes for predicting an intra-prediction mode of the current block of video data based on a location of the one or more blocks, wherein to identify the one or more blocks, the instructions cause the one or more processors to exclude locations of any block of the first largest coded unit;determine the one or more most probable intra-prediction modes based on respective intra-prediction modes of the identified one or more blocks; and code data that indicates the intra-prediction mode for the current block based on the one or more most-probable intra-prediction modes

18. The non-transitory computer-readable storage medium of claim 17, wherein the first largest coded unit and the second largest coded unit are included in a single slice of video data

19. The non-transitory computer-readable storage medium of claim 17, wherein to identify the one or more blocks, the instructions cause the one or more processors to identify one or more left-neighboring blocks of the current block.

20. The non-transitory computer-readable storage medium of claim 17, wherein to identify the one or more blocks, the instructions cause the one or more processors to identify a first left-neighboring first block and a second left-neighboring block that is positioned below the current block.

21. An apparatus for coding video data, the apparatus comprising: means for coding a first largest coded unit of a slice of video data;means for identifying, for a current block of video data that is positioned below the first largest coded unit and that neighbors the first largest coded unit and that is included in a second largest coded unit of the slice of video data, one or more blocks from which to determine one or more most probable intra-prediction modes for predicting an intra-prediction mode of the current block of video data based on a location of the one or more blocks, wherein the means for identifying the one or more blocks comprises means for excluding locations of any block of the first largest coded unit; means for determining the one or more most probable intra-prediction modes based on respective intra-prediction modes of the one or more blocks; and means for coding data that indicates the intra-prediction mode for the current block based on the one or more most-probable intra-prediction modes.

22. The apparatus of claim 21, wherein the first largest coded unit and the second largest coded unit are included in a single slice of video data.

23. The apparatus of claim 21, wherein the means for identifying the one or more blocks comprises means for identifying one or more left-neighboring blocks of the block.

24. The apparatus of claim 21, wherein the means for identifying the one or more blocks comprises means for identifying a first left-neighboring first block and a second left-neighboring block that is positioned below the block.

25. The method of claim 1, further comprising:determining, for a second block of video data that is included in the second largest coded unit and that is positioned below current block and that neighbors the current block, a most probable intra-prediction mode for predicting an intra-prediction mode of the second block based on the intra-prediction most of the current block; and coding data that indicates the intra-prediction mode of the second block based on the most-probable intra-prediction mode.

26. The apparatus of claim 9, wherein the one or more processors are further configured to:determine, for a second block of video data that is included in the second largest coded unit and that is positioned below current block and that neighbors the current block, a most probable intra-prediction mode for predicting an intra-prediction mode of the second block based on the intra-prediction most of the current block; and code data that indicates the intra-prediction mode of the second block based on the most-probable intra-prediction mode.

27. The non-transitory computer-readable medium of claim 17, wherein the instructions further cause the one or more processors to:determine, for a second block of video data that is included in the second largest coded unit and that is positioned below current block and that neighbors the current block, a most probable intra-prediction mode for predicting an intra-prediction mode of the second block based on the intra-prediction most of the current block; and code data that indicates the intra-prediction mode of the second block based on the most-probable intra-prediction mode.

28. The apparatus of claim 21, wherein the apparatus further comprises:means for determining, for a second block of video data that is included in the second largest coded unit and that is positioned below current block and that neighbors the current block, a most probable intra-prediction mode for predicting an intra-prediction mode of the second block based on the intra-prediction most of the current block; and means for coding data that indicates the intra-prediction mode of the second block based on the most-probable intra-prediction mode.']