Don't send touchcancel on touch scroll start

content/browser/renderer_host/input/input_router_impl.cc

 // Copyright 2013 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/input/input_router_impl.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 74 matching lines @@
 }
 #endif
 
 TouchEventQueue::TouchScrollingMode GetTouchScrollingMode() {
   std::string modeString = CommandLine::ForCurrentProcess()->
       GetSwitchValueASCII(switches::kTouchScrollingMode);
   if (modeString == switches::kTouchScrollingModeSyncTouchmove)
     return TouchEventQueue::TOUCH_SCROLLING_MODE_SYNC_TOUCHMOVE;
   if (modeString == switches::kTouchScrollingModeAbsorbTouchmove)
     return TouchEventQueue::TOUCH_SCROLLING_MODE_ABSORB_TOUCHMOVE;
-  if (modeString != "" &&
-      modeString != switches::kTouchScrollingModeTouchcancel)
+  if (modeString == switches::kTouchScrollingModeTouchcancel)
+    return TouchEventQueue::TOUCH_SCROLLING_MODE_TOUCHCANCEL;
+  if (modeString != "")
     LOG(ERROR) << "Invalid --touch-scrolling-mode option: " << modeString;
   return TouchEventQueue::TOUCH_SCROLLING_MODE_DEFAULT;
 }
 
 GestureEventWithLatencyInfo MakeGestureEvent(WebInputEvent::Type type,
                                              double timestamp_seconds,
                                              int x,
                                              int y,
                                              int modifiers,
                                              const ui::LatencyInfo latency) {
@@ skipping 698 matching lines @@
   touch_event_queue_->SetAckTimeoutEnabled(touch_ack_timeout_enabled,
                                            touch_ack_timeout_delay_ms_);
 }
 
 bool InputRouterImpl::IsInOverscrollGesture() const {
   OverscrollController* controller = client_->GetOverscrollController();
   return controller && controller->overscroll_mode() != OVERSCROLL_NONE;
 }
 
 }  // namespace content