gpu: Add YCbCr 420v extension.

gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_420v_image.txt

Index: gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_420v_image.txt
diff --git a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_422_image.txt b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_420v_image.txt
similarity index 73%
copy from gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_422_image.txt
copy to gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_420v_image.txt
index 546d783976d4c2e4ee8dea6b01afbb65c47102fa..3a5120b19adf7fbe32c14227a6be163249570bfb 100644
--- a/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_422_image.txt
+++ b/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_ycbcr_420v_image.txt
@@ -1,14 +1,14 @@
 Name
 
-    CHROMIUM_ycbcr_422_image
+    CHROMIUM_ycbcr_420v_image
 
 Name Strings
 
-    GL_CHROMIUM_ycbcr_422_image
+    GL_CHROMIUM_ycbcr_420v_image
 
 Version
 
-    Last Modifed Date: August 26, 2015
+    Last Modifed Date: October 26, 2015
 
 Dependencies
 
@@ -19,7 +19,7 @@ Dependencies
 Overview
 
     This extension provides a new internal image format to use when creating an 
-    image from underlying '2vuy' buffers. 
+    image from underlying '420v' buffers. 
 
     This extension is useful in conjunction with CreateImageCHROMIUM and
     CreateGpuMemoryBufferImageCHROMIUM to define the format of GpuMemoryBuffer 
@@ -37,7 +37,7 @@ New Tokens
     
     Accepted by the <internalformat> parameter of CreateImageCHROMIUM, and 
     <internalformat> parameter of CreateGpuMemoryBufferImageCHROMIUM:
-        GL_RGB_YCBCR_422_CHROMIUM 0x78FB
+        GL_RGB_YCBCR_420V_CHROMIUM 0x78FC
 
 New State
 
@@ -45,4 +45,4 @@ New State
 
 Revision History
 
-    8/26/2015   Documented the extension
+    10/26/2015   Documented the extension