Enable texture readback support for Android

content/common/gpu/client/gl_helper.h

Index: content/common/gpu/client/gl_helper.h
diff --git a/content/common/gpu/client/gl_helper.h b/content/common/gpu/client/gl_helper.h
index 8157c9a96bed913ece6b6a2ceaa4ff35fc6c3f66..9e58b5bf776959fcde2a180fd22e8bd3d29aa6af 100644
--- a/content/common/gpu/client/gl_helper.h
+++ b/content/common/gpu/client/gl_helper.h
@@ -39,10 +39,24 @@ class GLHelper {
                      unsigned char* out,
                      const base::Callback<void(bool)>& callback);
 
+  // Copies the raw texture data out of |texture| into |out|.  |size| is the
+  // size of the texture.  The texture is assumed to have a format of GL_RGBA
+  // with a pixel type of GL_UNSIGNED_BYTE.  This is a blocking call that calls
+  // glReadPixels on this current context.
+  void SyncCopyRawTextureTo(WebKit::WebGLId texture,

[piman, 2012/10/19 22:10:10]

I'm not sure what you mean by Raw.
This looks like CopyTextureTo except without cropping or scaling, and
synchronous.
Maybe rename CopyTextureTo into CropScaleAndReadbackTexture, whereas this one
would be ReadbackTextureSync, so that there's no confusion?

[David Trainor- moved to gerrit, 2012/10/19 22:33:54]

So CopyTextureTo seems to also potentially swizzle R and B/vertically flip the
image (inside WebGraphicsContext3D::readbackFramebuffer).  This version performs
no post operations on the texture it reads back for performance reasons.  It
uses readPixels instead of the utility method readbackFramebuffer.  I like the
name changes though.  I could go with CopyScaleReadbackAndCleanTexture
(mouthful, but accurate) and ReadbackTextureSync?

On 2012/10/19 22:10:10, piman wrote:

+                            const gfx::Size& size,
+                            unsigned char* out);
+
   // Creates a copy of the specified texture. |size| is the size of the texture.
   WebKit::WebGLId CopyTexture(WebKit::WebGLId texture,
                               const gfx::Size& size);
 
+  // Creates a scaled copy of the specified texture. |src_size| is the size of
+  // the texture and |dst_size| is the size of the resulting copy.
+  WebKit::WebGLId CopyTexture(WebKit::WebGLId texture,

[piman, 2012/10/19 22:10:10]

No overloading please. CopyAndScaleTexture?

[David Trainor- moved to gerrit, 2012/10/19 23:11:27]

Done.

+                              const gfx::Size& src_size,
+                              const gfx::Size& dst_size);
+
   // Returns the shader compiled from the source.
   WebKit::WebGLId CompileShaderFromSource(const WebKit::WGC3Dchar* source,
                                           WebKit::WGC3Denum type);