Enabled EXT_sRGB WebGL extension support in the command buffer.

gpu/command_buffer/common/gles2_cmd_utils.cc

Index: gpu/command_buffer/common/gles2_cmd_utils.cc
diff --git a/gpu/command_buffer/common/gles2_cmd_utils.cc b/gpu/command_buffer/common/gles2_cmd_utils.cc
index 3b5097cd43835dcd3ba5846a5be77dde4a5505b8..41db0b8143cf5d9eaf07035273f88b04222db926 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils.cc
+++ b/gpu/command_buffer/common/gles2_cmd_utils.cc
@@ -232,6 +232,10 @@ int GLES2Util::GLGetNumValuesReturned(int id) const {
     //    GL_EXT_multisampled_render_to_texture
     case GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_SAMPLES_EXT:
       return 1;
+    // -- glGetFramebufferAttachmentParameteriv with
+    //    GL_EXT_sRGB
+    case GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING_EXT:
+      return 1;
 
     // -- glGetProgramiv
     case GL_DELETE_STATUS:
@@ -352,11 +356,13 @@ int ElementsPerGroup(int format, int type) {
 
     switch (format) {
     case GL_RGB:
+    case GL_SRGB_EXT:
        return 3;
     case GL_LUMINANCE_ALPHA:
        return 2;
     case GL_RGBA:
     case GL_BGRA_EXT:
+    case GL_SRGB_ALPHA_EXT:
        return 4;
     case GL_ALPHA:
     case GL_LUMINANCE:
@@ -670,6 +676,7 @@ uint32 GLES2Util::GetChannelsForFormat(int format) {
     case GL_RGB565:
     case GL_RGB16F_EXT:
     case GL_RGB32F_EXT:
+    case GL_SRGB_EXT:
       return kRGB;
     case GL_BGRA_EXT:
     case GL_BGRA8_EXT:
@@ -679,6 +686,8 @@ uint32 GLES2Util::GetChannelsForFormat(int format) {
     case GL_RGBA8_OES:
     case GL_RGBA4:
     case GL_RGB5_A1:
+    case GL_SRGB_ALPHA_EXT:
+    case GL_SRGB8_ALPHA8_EXT:
       return kRGBA;
     case GL_DEPTH_COMPONENT32_OES:
     case GL_DEPTH_COMPONENT24_OES: