Fix frame coordinate translation issue with scroll views.

third_party/WebKit/Source/web/WebInputEventConversion.cpp

Index: third_party/WebKit/Source/web/WebInputEventConversion.cpp
diff --git a/third_party/WebKit/Source/web/WebInputEventConversion.cpp b/third_party/WebKit/Source/web/WebInputEventConversion.cpp
index 7b9defc7bf238a88ca6681c5367b07a8f38c8403..b30074369556e5b36a1629b59d02275f7c3f6d34 100644
--- a/third_party/WebKit/Source/web/WebInputEventConversion.cpp
+++ b/third_party/WebKit/Source/web/WebInputEventConversion.cpp
@@ -195,9 +195,17 @@ WebMouseEventBuilder::WebMouseEventBuilder(const FrameView* plugin_parent,
   if (event.NativeEvent()) {
     *static_cast<WebMouseEvent*>(this) =
         event.NativeEvent()->FlattenTransform();
-    WebFloatPoint absolute_root_frame_location = PositionInRootFrame();
-    IntPoint local_point = RoundedIntPoint(layout_item.AbsoluteToLocal(
-        absolute_root_frame_location, kUseTransforms));
+    WebFloatPoint absolute_location = PositionInRootFrame();
+
+    // TODO(dtapuska): |plugin_parent| should never be null. Remove this
+    // conditional code.
+    // Translate the root frame position to content coordinates.
+    if (plugin_parent) {
+      absolute_location = plugin_parent->RootFrameToContents(absolute_location);
+    }
+
+    IntPoint local_point = RoundedIntPoint(
+        layout_item.AbsoluteToLocal(absolute_location, kUseTransforms));
     SetPositionInWidget(local_point.X(), local_point.Y());
     return;
   }