Fix the scale of Drag and Drop shadow image.

content/browser/web_contents/web_contents_view_android.cc

Index: content/browser/web_contents/web_contents_view_android.cc
diff --git a/content/browser/web_contents/web_contents_view_android.cc b/content/browser/web_contents/web_contents_view_android.cc
index b0a5fb69c8e61d0e7ca3e7ca888d189595d6af04..ae913a3e415be14f5dc4d93e4a9fa5ed7de7df7b 100644
--- a/content/browser/web_contents/web_contents_view_android.cc
+++ b/content/browser/web_contents/web_contents_view_android.cc
@@ -249,8 +249,11 @@ void WebContentsViewAndroid::StartDragging(
   ScopedJavaLocalRef<jstring> jtext =
       ConvertUTF16ToJavaString(env, drop_data.text.string());
 
+  float page_scale = content_view_core_->page_scale();
+  // No way to scale image.bitmap() itself. So we need to pass the page scale
+  // here and let the embedder do the scaling.
   if (!native_view->StartDragAndDrop(
-          jtext, gfx::ConvertToJavaBitmap(image.bitmap()))) {
+          jtext, gfx::ConvertToJavaBitmap(image.bitmap()), page_scale)) {

[Ted C, 2016/09/20 20:05:24]

who generates the bitmap?

In this case, were we generating it to be too large?  If so, we should really
try to fix it at generation time to be scaled down to avoid passing a bigger
bitmap across to java (since it will use more memory for something we don't
actually need).

[hush (inactive), 2016/09/20 21:32:33]

Blink generates it here.
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/page/Drag...

It is not always bigger than what's needed though:
if page scale is < 1, the bitmap is bigger than necessary. Otherwise, it is
smaller than necessary.

     // Need to clear drag and drop state in blink.
     OnDragEnded();
     return;