[Reland] Fix ReadPixels from float fbo buffer in ES2/WebGL1.

gpu/command_buffer/common/gles2_cmd_utils.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file is here so other GLES2 related files can have a common set of
 // includes where appropriate.
 
 #include <sstream>
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
@@ skipping 1049 matching lines @@
     case GL_RGBA16I:
       return GL_SHORT;
     case GL_R32I:
     case GL_RG32I:
     case GL_RGBA32I:
       return GL_INT;
     case GL_R32F:
     case GL_RG32F:
     case GL_RGB32F:
     case GL_RGBA32F:
-      return GL_FLOAT;
+    case GL_R11F_G11F_B10F:
+      return GL_UNSIGNED_BYTE;
     case GL_R16F:
     case GL_RG16F:
-    case GL_R11F_G11F_B10F:
     case GL_RGB16F:
     case GL_RGBA16F:
-      // TODO(zmo): Consider return GL_UNSIGNED_INT_10F_11F_11F_REV and
-      // GL_HALF_FLOAT.
-      return GL_FLOAT;
-    case GL_RGBA:
-    case GL_RGB:
-      // Unsized internal format, check the type
-      switch (texture_type) {
-        case GL_FLOAT:
-        case GL_HALF_FLOAT_OES:
-          return GL_FLOAT;
-        // TODO(zmo): Consider return GL_UNSIGNED_SHORT_5_6_5,
-        // GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_5_5_5_1, and
-        // GL_UNSIGNED_INT_2_10_10_10_REV.
-        default:
-          return GL_UNSIGNED_BYTE;
-      }
+      return GL_HALF_FLOAT;
     default:
-      return GL_UNSIGNED_BYTE;
+      // Unsized internal format.
+      return texture_type;
   }
 }
 
 uint32_t GLES2Util::GetChannelsForFormat(int format) {
   switch (format) {
     case GL_ALPHA:
     case GL_ALPHA16F_EXT:
     case GL_ALPHA32F_EXT:
       return kAlpha;
     case GL_LUMINANCE:
@@ skipping 440 matching lines @@
   }
 
   return true;
 }
 
 #include "gpu/command_buffer/common/gles2_cmd_utils_implementation_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu