Move compositor InputHandler from RenderViewImpl to RenderWidget.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index d7559a11a91ee6dac61611d01011bc95558e7ce8..d78c1693eb86fadd921c82a2cca5bc98930c8d71 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -610,8 +610,19 @@ LayerTreeHostImpl::EventListenerTypeForTouchStartAt(
   LayerImpl* layer_impl =
       active_tree_->FindLayerThatIsHitByPointInTouchHandlerRegion(
           device_viewport_point);
-  if (layer_impl == NULL)
+  if (layer_impl == NULL) {
+    // At present, TouchHandlerRegions are only set for LayerTrees serving the
+    // document's mainframe, i.e. LayerTrees that have a ViewPort defined. But
+    // subframes can still have touch handlers, so here we err on the side of
+    // caution and report a handler even if we don't know which layer it's on.
+    if ((active_tree_->event_listener_properties(
+             EventListenerClass::kTouchStartOrMove) ==
+         EventListenerProperties::kBlocking) &&
+        !active_tree_->OuterViewportScrollLayer()) {
+      return InputHandler::TouchStartEventListenerType::HANDLER;
+    }
     return InputHandler::TouchStartEventListenerType::NO_HANDLER;
+  }
 
   if (!CurrentlyScrollingLayer())
     return InputHandler::TouchStartEventListenerType::HANDLER;