Implement GLHelperReadbackSupport for GLHelper usage.

content/common/gpu/client/gl_helper_unittest.cc

Index: content/common/gpu/client/gl_helper_unittest.cc
diff --git a/content/common/gpu/client/gl_helper_unittest.cc b/content/common/gpu/client/gl_helper_unittest.cc
index 91cfa2179f5261cb855609e567c514b9ed93d9bf..d259b8d0edfdf3111e1cdd591629dc300cb19e4e 100644
--- a/content/common/gpu/client/gl_helper_unittest.cc
+++ b/content/common/gpu/client/gl_helper_unittest.cc
@@ -1001,12 +1001,8 @@ class GLHelperTest : public testing::Test {
   bool TestTextureFormatReadback(const gfx::Size& src_size,
                          SkBitmap::Config bitmap_config,
                          bool async) {
-    DCHECK((bitmap_config == SkBitmap::kRGB_565_Config) ||
-           (bitmap_config == SkBitmap::kARGB_8888_Config));
-    bool rgb565_format = (bitmap_config == SkBitmap::kRGB_565_Config);
-    if (rgb565_format && !helper_->CanUseRgb565Readback()) {
-      LOG(INFO) << "RGB565 Format Not supported on this platform";
-      LOG(INFO) << "Skipping RGB565ReadBackTest";
+    if (!helper_->IsReadbackConfigSupported(bitmap_config)) {
+      LOG(INFO) << "Skipping test format not supported" << bitmap_config;
       return true;
     }
     WebGLId src_texture = context_->createTexture();