Add smoothness test for hover during trackpad scrolling [perf implications]

content/renderer/gpu/gpu_benchmarking_extension.cc

Index: content/renderer/gpu/gpu_benchmarking_extension.cc
diff --git a/content/renderer/gpu/gpu_benchmarking_extension.cc b/content/renderer/gpu/gpu_benchmarking_extension.cc
index 366d0a8b68aa219db1eab3446ce393848b4eefc8..27038d732042457f92bb8ef9693ad3bfb8a3848b 100644
--- a/content/renderer/gpu/gpu_benchmarking_extension.cc
+++ b/content/renderer/gpu/gpu_benchmarking_extension.cc
@@ -289,6 +289,22 @@ bool BeginSmoothScroll(v8::Isolate* isolate,
   if (!context.Init(false))
     return false;
 
+  // Convert coordinates from CSS pixels to density independent pixels (DIPs).
+  float page_scale_factor = context.web_view()->pageScaleFactor();
+
+  if (gesture_source_type == SyntheticGestureParams::MOUSE_INPUT) {
+    // Ensure the mouse is centered and visible, in case it will
+    // trigger any hover or mousemove effects.
+    blink::WebRect contentRect =
+        context.web_view()->mainFrame()->visibleContentRect();
+    blink::WebMouseEvent mouseMove;
+    mouseMove.type = blink::WebInputEvent::MouseMove;
+    mouseMove.x = (contentRect.x + contentRect.width / 2) * page_scale_factor;
+    mouseMove.y = (contentRect.y + contentRect.height / 2) * page_scale_factor;
+    context.web_view()->handleInputEvent(mouseMove);
+    context.web_view()->setCursorVisibilityState(true);
+  }
+
   scoped_refptr<CallbackAndContext> callback_and_context =
       new CallbackAndContext(
           isolate, callback, context.web_frame()->mainWorldScriptContext());
@@ -296,9 +312,6 @@ bool BeginSmoothScroll(v8::Isolate* isolate,
   scoped_ptr<SyntheticSmoothScrollGestureParams> gesture_params(
       new SyntheticSmoothScrollGestureParams);
 
-  // Convert coordinates from CSS pixels to density independent pixels (DIPs).
-  float page_scale_factor = context.web_view()->pageScaleFactor();
-
   if (gesture_source_type < 0 ||
       gesture_source_type > SyntheticGestureParams::GESTURE_SOURCE_TYPE_MAX) {
     return false;