UMA metrics for use count of wheel and touch scrolls.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 2672 matching lines @@
   // in input_handler_proxy instead.
   wheel_scrolling_ = IsWheelBasedScroll(type);
   scroll_state->set_is_direct_manipulation(!wheel_scrolling_);
   // Invoke |DistributeScrollDelta| even with zero delta and velocity to ensure
   // scroll customization callbacks are invoked.
   DistributeScrollDelta(scroll_state);
 
   client_->RenewTreePriority();
   RecordCompositorSlowScrollMetric(type, CC_THREAD);
 
+  UpdateScrollSourceInfo(wheel_scrolling_);
+
   return scroll_status;
 }
 
 InputHandler::ScrollStatus LayerTreeHostImpl::RootScrollBegin(
     ScrollState* scroll_state,
     InputHandler::ScrollInputType type) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::RootScrollBegin");
 
   ClearCurrentlyScrollingNode();
 
@@ skipping 776 matching lines @@
   CollectScrollDeltas(scroll_info.get(), active_tree_.get());
   CollectScrollbarUpdates(scroll_info.get(), &scrollbar_animation_controllers_);
   scroll_info->page_scale_delta =
       active_tree_->page_scale_factor()->PullDeltaForMainThread();
   scroll_info->top_controls_delta =
       active_tree()->top_controls_shown_ratio()->PullDeltaForMainThread();
   scroll_info->elastic_overscroll_delta =
       active_tree_->elastic_overscroll()->PullDeltaForMainThread();
   scroll_info->swap_promises.swap(swap_promises_for_main_thread_scroll_update_);
 
+  // Record and reset scroll source flags.
+  scroll_info->has_scrolled_by_wheel = has_scrolled_by_wheel_;
+  scroll_info->has_scrolled_by_touch = has_scrolled_by_touch_;
+  has_scrolled_by_wheel_ = has_scrolled_by_touch_ = false;
+
   return scroll_info;
 }
 
 void LayerTreeHostImpl::SetFullViewportDamage() {
   SetViewportDamage(gfx::Rect(DrawViewportSize()));
 }
 
 bool LayerTreeHostImpl::AnimatePageScale(base::TimeTicks monotonic_time) {
   if (!page_scale_animation_)
     return false;
@@ skipping 682 matching lines @@
     if (is_visible) {
       worker_context_visibility_ =
           worker_context->CacheController()->ClientBecameVisible();
     } else {
       worker_context->CacheController()->ClientBecameNotVisible(
           std::move(worker_context_visibility_));
     }
   }
 }
 
+void LayerTreeHostImpl::UpdateScrollSourceInfo(bool is_wheel_scroll) {
+  if (is_wheel_scroll)
+    has_scrolled_by_wheel_ = true;
+  else
+    has_scrolled_by_touch_ = true;
+}
+
 }  // namespace cc