Fix WebKeyboardEvent interruption of compositor scrolling

content/renderer/input/input_handler_proxy.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/renderer/input/input_handler_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 232 matching lines @@
       if (touch_event.touches[i].state != WebTouchPoint::StatePressed)
         continue;
       if (input_handler_->HaveTouchEventHandlersAt(
               gfx::Point(touch_event.touches[i].position.x,
                          touch_event.touches[i].position.y))) {
         return DID_NOT_HANDLE;
       }
     }
     return DROP_EVENT;
   } else if (WebInputEvent::isKeyboardEventType(event.type)) {
-    CancelCurrentFling(true);
+    // Only call |CancelCurrentFling()| if a fling was active, as it will
+    // otherwise disrupt an in-progress touch scroll.
+    if (fling_curve_)
+      CancelCurrentFling(true);
   } else if (event.type == WebInputEvent::MouseMove) {
     const WebMouseEvent& mouse_event =
         *static_cast<const WebMouseEvent*>(&event);
     // TODO(tony): Ignore when mouse buttons are down?
     // TODO(davemoore): This should never happen, but bug #326635 showed some
     // surprising crashes.
     CHECK(input_handler_);
     input_handler_->MouseMoveAt(gfx::Point(mouse_event.x, mouse_event.y));
   }
 
@@ skipping 245 matching lines @@
 
   if (did_scroll) {
     fling_parameters_.cumulativeScroll.width += clipped_increment.width;
     fling_parameters_.cumulativeScroll.height += clipped_increment.height;
   }
 
   return did_scroll;
 }
 
 }  // namespace content