android: add ThumbnailCache

content/browser/android/content_readback_handler.cc

Index: content/browser/android/content_readback_handler.cc
diff --git a/content/browser/android/content_readback_handler.cc b/content/browser/android/content_readback_handler.cc
index 601e3a317283eb1332a1e9fcb77c0f6dd2d157ab..ba1ba9ffc6b10525b3642e052f8d1d154a05b95b 100644
--- a/content/browser/android/content_readback_handler.cc
+++ b/content/browser/android/content_readback_handler.cc
@@ -69,8 +69,9 @@ void ContentReadbackHandler::GetContentBitmap(JNIEnv* env,
                  weak_factory_.GetWeakPtr(),
                  readback_id);
 
+  SkColorType sk_color_type = gfx::ConvertToSkiaColorType(color_type);
   view->GetScaledContentBitmap(
-      scale, color_type, gfx::Rect(x, y, width, height), result_callback);
+      scale, sk_color_type, gfx::Rect(x, y, width, height), result_callback);
 }
 
 void ContentReadbackHandler::GetCompositorBitmap(JNIEnv* env,