Prepare SyntheticPointerAction to handle mouse actions

content/common/input/synthetic_pointer_action_params.h

 // Copyright 2016 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 CONTENT_COMMON_INPUT_SYNTHETIC_POINTER_ACTION_PARAMS_H_
 #define CONTENT_COMMON_INPUT_SYNTHETIC_POINTER_ACTION_PARAMS_H_
 
 #include "base/logging.h"
 #include "content/common/content_export.h"
 #include "content/common/input/input_param_traits.h"
@@ skipping 33 matching lines @@
   static const SyntheticPointerActionParams* Cast(
       const SyntheticGestureParams* gesture_params);
 
   void set_pointer_action_type(PointerActionType pointer_action_type) {
     pointer_action_type_ = pointer_action_type;
   }
 
   void set_index(int index) {
     DCHECK(pointer_action_type_ != PointerActionType::PROCESS &&
            pointer_action_type_ != PointerActionType::FINISH);
+    // For all mouse pointer actions, the index should always be 0.
+    DCHECK(gesture_source_type != MOUSE_INPUT || index == 0);
     index_ = index;
   }
 
   void set_position(const gfx::PointF& position) {
     DCHECK(pointer_action_type_ == PointerActionType::PRESS ||
            pointer_action_type_ == PointerActionType::MOVE);
     position_ = position;
   }
 
   PointerActionType pointer_action_type() const { return pointer_action_type_; }
 
   int index() const {
     DCHECK(pointer_action_type_ != PointerActionType::PROCESS &&
            pointer_action_type_ != PointerActionType::FINISH);
+    DCHECK(gesture_source_type != MOUSE_INPUT || index_ == 0);
     return index_;
   }
 
   gfx::PointF position() const {
     DCHECK(pointer_action_type_ == PointerActionType::PRESS ||
            pointer_action_type_ == PointerActionType::MOVE);
     return position_;
   }
 
  private:
   friend struct IPC::ParamTraits<content::SyntheticPointerActionParams>;
   friend struct ipc_fuzzer::FuzzTraits<content::SyntheticPointerActionParams>;
 
   PointerActionType pointer_action_type_;
   // Pass a position value when sending a press or move action.
   gfx::PointF position_;
   // Pass an index value except if the pointer_action_type_ is PROCESS.
   int index_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_INPUT_SYNTHETIC_POINTER_ACTION_PARAMS_H_