Allow task pools to reason about transparency.

cc/resources/resource_format.cc

Index: cc/resources/resource_format.cc
diff --git a/cc/resources/resource_format.cc b/cc/resources/resource_format.cc
index c62ae934d728f5d749514164f5da80fc9094c4bd..f5959dce364f8e07847d9acc9f4c683907174e92 100644
--- a/cc/resources/resource_format.cc
+++ b/cc/resources/resource_format.cc
@@ -106,4 +106,29 @@ gfx::BufferFormat BufferFormat(ResourceFormat format) {
   return gfx::BufferFormat::RGBA_8888;
 }
 
+ResourceFormat BufferFormatToResourceFormat(gfx::BufferFormat format) {
+  switch (format) {
+    case gfx::BufferFormat::RGBA_8888:
+      return RGBA_8888;
+    case gfx::BufferFormat::BGRA_8888:
+      return BGRA_8888;
+    case gfx::BufferFormat::RGBA_4444:
+      return RGBA_4444;
+    case gfx::BufferFormat::ETC1:
+      return ETC1;
+    case gfx::BufferFormat::ATC:
+    case gfx::BufferFormat::ATCIA:
+    case gfx::BufferFormat::DXT1:
+    case gfx::BufferFormat::DXT5:
+    case gfx::BufferFormat::R_8:
+    case gfx::BufferFormat::BGRX_8888:
+    case gfx::BufferFormat::YUV_420:
+    case gfx::BufferFormat::YUV_420_BIPLANAR:
+    case gfx::BufferFormat::UYVY_422:
+      break;
+  }
+  NOTREACHED();
+  return RGBA_8888;
+}
+
 }  // namespace cc