cc: Fix R_8 GpuMemoryBuffers

cc/resources/resource_format.cc

Index: cc/resources/resource_format.cc
diff --git a/cc/resources/resource_format.cc b/cc/resources/resource_format.cc
index c62ae934d728f5d749514164f5da80fc9094c4bd..84dce657bd1330b6af0f0092b940677adaf858dc 100644
--- a/cc/resources/resource_format.cc
+++ b/cc/resources/resource_format.cc
@@ -4,8 +4,7 @@
 
 #include "cc/resources/resource_format.h"
 
-#include "third_party/khronos/GLES2/gl2.h"
-#include "third_party/khronos/GLES2/gl2ext.h"
+#include "ui/gl/gl_bindings.h"
 
 namespace cc {
 
@@ -87,19 +86,26 @@ GLenum GLInternalFormat(ResourceFormat format) {
   return GLDataFormat(format);
 }
 
+GLenum GLImageFormat(ResourceFormat format) {
+  if (format == RED_8)
+    return GL_R8_EXT;

[reveman, 2015/11/05 13:46:01]

Can we have normal textures use GL_R8_EXT as well? I don't think there's any
good reason for why we should have to special case this for GLImage.

[ccameron, 2015/11/05 19:09:20]

That was the first thing that I tried, but GL_R8_EXT doesn't go through the
various validators.

In particular, if we check out the GLES extension text:
https://www.khronos.org/registry/gles/extensions/EXT/EXT_texture_rg.txt
New Tokens
    Accepted by the <internalformat> parameter of TexImage2D and CopyTexImage2D,
    and the <format> parameter of TexImage2D, TexSubImage2D, and ReadPixels:
        RED_EXT                 0x1903
        RG_EXT                  0x8227
    Accepted by the <internalformat> parameter of RenderbufferStorage and
    RenderbufferStorageMultisampleAPPLE:
        R8_EXT                  0x8229
        RG8_EXT                 0x822B
So according to the extension spec, R8_EXT is not a valid argument for <format>
or <internalformat> for TexImage2D.

FWIW, for the related desktop GL extension text:
https://www.opengl.org/registry/specs/ARB/texture_rg.txt
It says that R8_ARB (which coincides with R8_EXT) is accepted as
<internalformat> but not <format>. I don't think that's relevant here because
the client code should be GLES and not desktop GL.

So I think that this is the right thing to do.

+  return GLInternalFormat(format);
+}
+
 gfx::BufferFormat BufferFormat(ResourceFormat format) {
   switch (format) {
-    case RGBA_8888:
-      return gfx::BufferFormat::RGBA_8888;
     case BGRA_8888:
       return gfx::BufferFormat::BGRA_8888;
+    case RED_8:
+      return gfx::BufferFormat::R_8;
     case RGBA_4444:
       return gfx::BufferFormat::RGBA_4444;
+    case RGBA_8888:
+      return gfx::BufferFormat::RGBA_8888;
     case ALPHA_8:
     case LUMINANCE_8:
     case RGB_565:
     case ETC1:
-    case RED_8:
       break;
   }
   NOTREACHED();