Fixed ui::TouchEvent rotation angle out-of-bound issue.

ui/events/gestures/motion_event_aura.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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/gestures/motion_event_aura.h"
 
 #include <cmath>
@@ skipping 10 matching lines @@
   pointer_properties.y = touch.y();
   pointer_properties.raw_x = touch.root_location_f().x();
   pointer_properties.raw_y = touch.root_location_f().y();
   pointer_properties.id = touch.touch_id();
   pointer_properties.pressure = touch.force();
   pointer_properties.source_device_id = touch.source_device_id();
 
   float radius_x = touch.radius_x();
   float radius_y = touch.radius_y();
   float rotation_angle_rad = touch.rotation_angle() * M_PI / 180.f;
+
   DCHECK_GE(radius_x, 0) << "Unexpected x-radius < 0";
   DCHECK_GE(radius_y, 0) << "Unexpected y-radius < 0";
-  DCHECK(0 <= rotation_angle_rad && rotation_angle_rad <= M_PI_2)
+  DCHECK(0 <= rotation_angle_rad && rotation_angle_rad < M_PI)
       << "Unexpected touch rotation angle";
 
+  // Make the angle acute to ease subsequent logic. The angle range effectively
+  // changes from [0, pi) to [0, pi/2).
+  if (rotation_angle_rad >= M_PI_2) {
+    rotation_angle_rad -= static_cast<float>(M_PI_2);
+    std::swap(radius_x, radius_y);
+  }
+
   if (radius_x > radius_y) {
     // The case radius_x == radius_y is omitted from here on purpose: for
     // circles, we want to pass the angle (which could be any value in such
     // cases but always seem to be set to zero) unchanged.
     pointer_properties.touch_major = 2.f * radius_x;
     pointer_properties.touch_minor = 2.f * radius_y;
     pointer_properties.orientation = rotation_angle_rad - M_PI_2;
   } else {
     pointer_properties.touch_major = 2.f * radius_y;
     pointer_properties.touch_minor = 2.f * radius_x;
@@ skipping 137 matching lines @@
 }
 
 int MotionEventAura::GetIndexFromId(int id) const {
   int index = FindPointerIndexOfId(id);
   DCHECK_GE(index, 0);
   DCHECK_LT(index, static_cast<int>(GetPointerCount()));
   return index;
 }
 
 }  // namespace ui