Manually compute inverted matrix for screen rotation

ui/base/events/event.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_BASE_EVENTS_EVENT_H_
 #define UI_BASE_EVENTS_EVENT_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/event_types.h"
@@ skipping 251 matching lines @@
   }
   gfx::Point root_location() const { return root_location_; }
 
   bool valid_system_location() const { return valid_system_location_; }
   void set_system_location(const gfx::Point& loc) {
     valid_system_location_ = true;
     system_location_ = loc;
   }
   const gfx::Point& system_location() const { return system_location_; }
 
-  // Applies |root_transform| to the event.
+  // Transform the locations using |inverted_root_transform|.
   // This is applied to both |location_| and |root_location_|.
-  virtual void UpdateForRootTransform(const gfx::Transform& root_transform);
+  virtual void UpdateForRootTransform(
+      const gfx::Transform& inverted_root_transform);
 
   template <class T> void ConvertLocationToTarget(T* source, T* target) {
     if (target && target != source)
       T::ConvertPointToTarget(source, target, &location_);
   }
 
  protected:
   explicit LocatedEvent(const base::NativeEvent& native_event);
 
   // Create a new LocatedEvent which is identical to the provided model.
@@ skipping 424 matching lines @@
   // This value is stored as a bitfield because the number of touch ids varies,
   // but we currently don't need more than 32 touches at a time.
   const unsigned int touch_ids_bitfield_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureEvent);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_EVENTS_EVENT_H_