Use GLHelper support to validate format before processing texture.

components/display_compositor/gl_helper_readback_support.cc

 // Copyright 2014 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.
 
 #include "base/logging.h"
 #include "components/display_compositor/gl_helper_readback_support.h"
 #include "gpu/GLES2/gl2extchromium.h"
 #include "third_party/skia/include/core/SkImageInfo.h"
 
 namespace display_compositor {
 
 GLHelperReadbackSupport::GLHelperReadbackSupport(gpu::gles2::GLES2Interface* gl)
     : gl_(gl) {
   InitializeReadbackSupport();
 }
 
 GLHelperReadbackSupport::~GLHelperReadbackSupport() {}
 
 void GLHelperReadbackSupport::InitializeReadbackSupport() {
   // We are concerned about 16, 32-bit formats only.  The below are the most
   // used 16, 32-bit formats.  In future if any new format support is needed
   // that should be added here.  Initialize the array with
   // GLHelperReadbackSupport::NOT_SUPPORTED as we dont know the supported
   // formats yet.
   for (int i = 0; i <= kLastEnum_SkColorType; ++i) {
     format_support_table_[i] = GLHelperReadbackSupport::NOT_SUPPORTED;
   }
-  // TODO(sikugu): kAlpha_8_SkColorType support check is failing on mesa.
-  // See crbug.com/415667.
+  CheckForReadbackSupport(kAlpha_8_SkColorType);
   CheckForReadbackSupport(kRGB_565_SkColorType);
   CheckForReadbackSupport(kARGB_4444_SkColorType);
   CheckForReadbackSupport(kRGBA_8888_SkColorType);
   CheckForReadbackSupport(kBGRA_8888_SkColorType);
   // Further any formats, support should be checked here.
 }
 
 void GLHelperReadbackSupport::CheckForReadbackSupport(
     SkColorType texture_format) {
   bool supports_format = false;
   switch (texture_format) {
+    case kAlpha_8_SkColorType:
+      supports_format = SupportsFormat(GL_ALPHA, GL_UNSIGNED_BYTE);
+      break;
     case kRGB_565_SkColorType:
       supports_format = SupportsFormat(GL_RGB, GL_UNSIGNED_SHORT_5_6_5);
       break;
     case kRGBA_8888_SkColorType:
       // This is the baseline, assume always true.
       supports_format = true;
       break;
     case kBGRA_8888_SkColorType:
       supports_format = SupportsFormat(GL_BGRA_EXT, GL_UNSIGNED_BYTE);
       break;
@@ skipping 66 matching lines @@
 GLHelperReadbackSupport::GetReadbackConfig(SkColorType color_type,
                                            bool can_swizzle,
                                            GLenum* format,
                                            GLenum* type,
                                            size_t* bytes_per_pixel) {
   DCHECK(format && type && bytes_per_pixel);
   *bytes_per_pixel = 4;
   *type = GL_UNSIGNED_BYTE;
   GLenum new_format = 0, new_type = 0;
   switch (color_type) {
+    case kAlpha_8_SkColorType:
+      if (format_support_table_[color_type] ==
+          GLHelperReadbackSupport::SUPPORTED) {
+        *format = GL_ALPHA;
+        *type = GL_UNSIGNED_BYTE;
+        *bytes_per_pixel = 1;
+        return GLHelperReadbackSupport::SUPPORTED;
+      }
+
+      break;
     case kRGB_565_SkColorType:
       if (format_support_table_[color_type] ==
           GLHelperReadbackSupport::SUPPORTED) {
         *format = GL_RGB;
         *type = GL_UNSIGNED_SHORT_5_6_5;
         *bytes_per_pixel = 2;
         return GLHelperReadbackSupport::SUPPORTED;
       }
       break;
     case kRGBA_8888_SkColorType:
@@ skipping 26 matching lines @@
       return GLHelperReadbackSupport::NOT_SUPPORTED;
     default:
       NOTREACHED();
       break;
   }
 
   return GLHelperReadbackSupport::NOT_SUPPORTED;
 }
 
 }  // namespace display_compositor