Fix bounding box calculation for touches with radius of 0.

ui/events/gesture_detection/gesture_provider.cc

 // Copyright 2014 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 "ui/events/gesture_detection/gesture_provider.h"
 
 #include <cmath>
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
@@ skipping 13 matching lines @@
     case MotionEvent::ACTION_POINTER_UP:   return "ACTION_POINTER_UP";
     case MotionEvent::ACTION_DOWN:         return "ACTION_DOWN";
     case MotionEvent::ACTION_UP:           return "ACTION_UP";
     case MotionEvent::ACTION_CANCEL:       return "ACTION_CANCEL";
     case MotionEvent::ACTION_MOVE:         return "ACTION_MOVE";
   }
   return "";
 }
 
 gfx::RectF GetBoundingBox(const MotionEvent& event) {
-  gfx::RectF bounds;
+  // Can't use gfx::RectF::Union, as it ignores touches with a radius of 0.
+  float left = std::numeric_limits<float>::max();
+  float top = std::numeric_limits<float>::max();
+  float right = -std::numeric_limits<float>::max();
+  float bottom = -std::numeric_limits<float>::max();
   for (size_t i = 0; i < event.GetPointerCount(); ++i) {
     float diameter = event.GetTouchMajor(i);
-    bounds.Union(gfx::RectF(event.GetX(i) - diameter / 2,
-                            event.GetY(i) - diameter / 2,
-                            diameter,
-                            diameter));
+    float x = event.GetX(i) - diameter / 2;
+    float y = event.GetY(i) - diameter / 2;
+    left = std::min(left, x);
+    right = std::max(right, x + diameter);
+    top = std::min(top, y);
+    bottom = std::max(bottom, y + diameter);
   }
-  return bounds;
+  return gfx::RectF(left, top, right - left, bottom - top);
 }
 
 GestureEventData CreateGesture(const GestureEventDetails& details,
                                int motion_event_id,
                                base::TimeTicks time,
                                float x,
                                float y,
                                float raw_x,
                                float raw_y,
                                size_t touch_point_count,
@@ skipping 760 matching lines @@
   if (current_down_event_)
     return;
 
   const bool double_tap_enabled = double_tap_support_for_page_ &&
                                   double_tap_support_for_platform_;
   gesture_listener_->SetDoubleTapEnabled(double_tap_enabled);
   scale_gesture_listener_->SetDoubleTapEnabled(double_tap_enabled);
 }
 
 }  //  namespace ui