Add code to collect crash data for https://crbug.com/592319.

content/browser/renderer_host/render_widget_host_input_event_router.cc

 // Copyright 2015 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 "content/browser/renderer_host/render_widget_host_input_event_router.h"
 
+#include "base/debug/dump_without_crashing.h"
 #include "cc/quads/surface_draw_quad.h"
 #include "cc/surfaces/surface_id_allocator.h"
 #include "cc/surfaces/surface_manager.h"
 #include "content/browser/renderer_host/render_widget_host_view_base.h"
 #include "content/common/frame_messages.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 
 namespace {
 
 void TransformEventTouchPositions(blink::WebTouchEvent* event,
@@ skipping 66 matching lines @@
     const gfx::Point& point_in_quad_space) {
   auto it = hittest_data_.find(surface_quad->surface_id);
   if (it != hittest_data_.end() && !it->second.ignored_for_hittest)
     return true;
   return false;
 }
 
 RenderWidgetHostInputEventRouter::RenderWidgetHostInputEventRouter()
     : touch_target_(nullptr),
       gesture_target_(nullptr),
-      active_touches_(0) {}
+      active_touches_(0),
+      number_of_gesture_targets_enqueued_(0),
+      number_of_gesture_targets_dequeued_(0),
+      last_gesture_event_index_(0),
+      last_touch_event_index_(0) {
+  for (unsigned i = 0; i < kNumLastEventTypes; ++i) {
+    last_gesture_event_types_[i] = blink::WebInputEvent::Undefined;
+    last_touch_event_types_[i] = blink::WebInputEvent::Undefined;
+  }
+}
 
 RenderWidgetHostInputEventRouter::~RenderWidgetHostInputEventRouter() {
   // We may be destroyed before some of the owners in the map, so we must
   // remove ourself from their observer lists.
   ClearAllObserverRegistrations();
 }
 
 RenderWidgetHostViewBase* RenderWidgetHostInputEventRouter::FindEventTarget(
     RenderWidgetHostViewBase* root_view,
     const gfx::Point& point,
@@ skipping 59 matching lines @@
 void RenderWidgetHostInputEventRouter::RouteGestureEvent(
     RenderWidgetHostViewBase* root_view,
     blink::WebGestureEvent* event,
     const ui::LatencyInfo& latency) {
   // We use GestureTapDown to detect the start of a gesture sequence since there
   // is no WebGestureEvent equivalent for ET_GESTURE_BEGIN. Note that this
   // means the GestureFlingCancel that always comes between ET_GESTURE_BEGIN and
   // GestureTapDown is sent to the previous target, in case it is still in a
   // fling.
   if (event->type == blink::WebInputEvent::GestureTapDown) {
-    DCHECK(!gesture_target_queue_.empty());
+    if (gesture_target_queue_.empty()) {
+      // Collect data to assist debugging https://crbug.com/592319.
+      // We'll assume for now if there's no target that we should just ignore
+      // the event.
+      LOG(ERROR) << "Gesture sequence start detected with no target available.";
+      base::debug::DumpWithoutCrashing();
+      return;
+    }
+
     const GestureTargetData& data = gesture_target_queue_.front();
     gesture_target_ = data.target;
     gesture_delta_ = data.delta;
     gesture_target_queue_.pop_front();
+    // Code to assist debugging https://crbug.com/592319.
+    number_of_gesture_targets_dequeued_++;
   }
 
+  // Code to assist debugging https://crbug.com/592319.
+  last_gesture_event_types_[last_gesture_event_index_] = event->type;
+  last_gesture_event_index_ =
+      (last_gesture_event_index_ + 1) % kNumLastEventTypes;

[tdresser, 2016/03/09 19:53:45]

Based on the code here, isn't last_gesture_event_index actually
next_gesture_event_index?

[wjmaclean, 2016/03/09 21:28:31]

Done.

+
   if (!gesture_target_)
     return;
 
   event->x += gesture_delta_.x();
   event->y += gesture_delta_.y();
   gesture_target_->ProcessGestureEvent(*event, latency);
 }
 
 void RenderWidgetHostInputEventRouter::RouteTouchEvent(
     RenderWidgetHostViewBase* root_view,
     blink::WebTouchEvent* event,
     const ui::LatencyInfo& latency) {
+  // Code to assist debugging https://crbug.com/592319.
+  last_touch_event_types_[last_touch_event_index_] = event->type;
+  last_touch_event_index_ =
+      (last_touch_event_index_ + 1) % kNumLastEventTypes;

[tdresser, 2016/03/09 19:53:45]

Looks like this is next_touch_event_index_.

[wjmaclean, 2016/03/09 21:28:31]

Done.

+
   switch (event->type) {
     case blink::WebInputEvent::TouchStart: {
       if (!active_touches_) {
         // Since this is the first touch, it defines the target for the rest
         // of this sequence.
         DCHECK(!touch_target_);
         gfx::Point transformed_point;
         gfx::Point original_point(event->touches[0].position.x,
                                   event->touches[0].position.y);
         touch_target_ =
             FindEventTarget(root_view, original_point, &transformed_point);
 
         // TODO(wjmaclean): Instead of just computing a delta, we should extract
         // the complete transform. We assume it doesn't change for the duration
         // of the touch sequence, though this could be wrong; a better approach
         // might be to always transform each point to the touch_target_
         // for the duration of the sequence.
         touch_delta_ = transformed_point - original_point;
         gesture_target_queue_.emplace_back(touch_target_, touch_delta_);
+        // Code to assist debugging https://crbug.com/592319.
+        number_of_gesture_targets_enqueued_++;
 
         if (!touch_target_)
           return;
       }
       ++active_touches_;
       if (touch_target_) {
         TransformEventTouchPositions(event, touch_delta_);
         touch_target_->ProcessTouchEvent(*event, latency);
       }
       break;
@@ skipping 54 matching lines @@
   if (owner_map_.find(cc::SurfaceIdAllocator::NamespaceForId(
           params.surface_id)) == owner_map_.end()) {
     return;
   }
   HittestData data;
   data.ignored_for_hittest = params.ignored_for_hittest;
   hittest_data_[params.surface_id] = data;
 }
 
 }  // namespace content