Update GL_IMPLEMENTATION_COLOR_READ_FORMAT for BGRA

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 bc39543385e9725f149da6809caa2b367e414b95..639ab0c9717fcb3c034281307486a88201942e13 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils.cc
+++ b/gpu/command_buffer/common/gles2_cmd_utils.cc
@@ -978,8 +978,13 @@ size_t GLES2Util::GLTargetToFaceIndex(uint32_t target) {
   }
 }
 
-uint32_t GLES2Util::GetGLReadPixelsImplementationFormat(
-    uint32_t internal_format) {
+uint32_t GLES2Util::GetGLReadPixelsAdditionalFormat(uint32_t internal_format,
+                                                    uint32_t texture_type) {
+  // GL_RGBA is supported by default. According to the spec, this function
+  // should return a second, implementaiton-chosen format. For consumers of

[piman, 2016/03/04 20:55:36]

typo: implementaiton->implementation

+  // this API to get the most benefit (as many efficient options as
+  // possible), this function attempts to return a non GL_RGBA format in
+  // cases where GL_RGBA would be returned.
   switch (internal_format) {
     case GL_R8:
     case GL_R16F:
@@ -1018,13 +1023,25 @@ uint32_t GLES2Util::GetGLReadPixelsImplementationFormat(
     case GL_RGBA32UI:
     case GL_RGBA32I:
       return GL_RGBA_INTEGER;
+    case GL_RGBA:
+    case GL_RGBA8:
+    case GL_BGRA_EXT:
+    case GL_BGRA8_EXT:
+      // We would return GL_RGBA here, but that is uninteresting, as it is
+      // supported by default. If the texture's type is GL_UNSIGNED_BYTE, we
+      // can also support GL_BGRA_EXT, so return this as another option.
+      if (texture_type == GL_UNSIGNED_BYTE)
+        return GL_BGRA_EXT;

[piman, 2016/03/04 20:55:37]

We're only allowed to return this if we expose GL_EXT_read_format_bgra to the
client - otherwise, the client would try to use it, but glReadPixels would fail.
See the code around enable_read_format_bgra in feature_info.cc

+      else
+        return GL_RGBA;
     default:
       return GL_RGBA;
   }
 }
 
-uint32_t GLES2Util::GetGLReadPixelsImplementationType(uint32_t internal_format,
-                                                      uint32_t texture_type) {
+uint32_t GLES2Util::GetGLReadPixelsTypeForAdditionalFormat(
+    uint32_t internal_format,
+    uint32_t texture_type) {
   switch (internal_format) {
     case GL_R16UI:
     case GL_RG16UI: