Enable CopyTextureCHROMIUM in Blink for Tex{Sub}Image2D with more cases

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index a3da846049bfe5db49feaba7ced2aecc5124e88d..7101f3c3d2f350f54b75502f75f50db998427cdd 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -637,11 +637,13 @@ bool WebGL2RenderingContextBase::canUseTexImageByGPU(
     GLint internalformat,
     GLenum type) {
   switch (internalformat) {
-    case GL_RGB565:
-    case GL_RGBA4:
+#if OS(MACOSX)
+    // RGB5_A1 is not color-renderable on NVIDIA Mac, see crbug.com/676209.
     case GL_RGB5_A1:

[Zhenyao Mo, 2017/03/10 00:10:23]

I am wondering if we can push this to the command buffer side and still go down
the GPU path (a different path in Mac).

[qiankun, 2017/03/10 02:48:04]

We can add a readback path for such formats, for example RGB5_A1 and RGB9_E5.
This is a TODO for CopyTextureCHROMIUM in command buffer.

-      // FIXME: ES3 limitation that CopyTexImage with sized internalformat,
-      // component sizes have to match the source color format.
+#endif
+    // TODO(qiankun.miao@intel.com): in ES3, component sizes have to match the
+    // source color format for CopyTexImage with sized internalformat.
+    case GL_RGB9_E5:

[Zhenyao Mo, 2017/03/10 00:10:23]

I am not sure about this. Again, I thought such color bit matching requirement
is only for fixed point formats, not for floats.

Otherwise, there won't a format that can match with RGB9_E5.

[qiankun, 2017/03/10 02:48:04]

RGB9_5 can also run the readback path.
I think color bit matching rule doesn't only apply to fixed point formats, see
following statements in ES 3.0.5 spec:
"
If internalformat is sized, the internal format of the new texel array is
internalformat,
and this is also the new texel array’s effective internal format. If the
component sizes of internalformat do not exactly match the corresponding
component
sizes of the source buffer’s effective internal format, described below, an
INVALID_OPERATION error is generated.
"

"
Calling CopyTexSubImage3D, CopyTexImage2D, or CopyTexSubImage2D
will result in an INVALID_OPERATION error if any of the following conditions
is true:
• internalformat of the texel array being (re)specified is RGB9_E5,
"

       return false;
     default:
       break;