Update Gamepad API to match the latest specification

ppapi/api/ppb_gamepad.idl

 /* 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.
  */
 
 /**
  * This file defines the <code>PPB_Gamepad</code> interface, which
  * provides access to gamepad devices.
  */
 
 [generate_thunk]
 
 label Chrome {
-  M19 = 1.0
+  M19 = 1.0,
+  M36 = 1.1
 };
 
 /**
  * The data for one gamepad device.
  */
-[assert_size(472)]
+[assert_size(672)]
 struct PP_GamepadSampleData {
     /**
      * Number of valid elements in the |axes| array.
      */
     uint32_t axes_length;
 
     /**
      * Normalized values for the axes, indices valid up to |axes_length|-1. Axis
      * values range from -1..1, and are in order of "importance".
      */
+    [version = 1.0]
     float_t[16] axes;
 
     /**
+     * Normalized values for the axes, indices valid up to |axes_length|-1. Axis
+     * values range from -1..1, and are in order of "importance".
+     */
+    [version = 1.1]
+    double_t[16] axes;
+
+    /**
      * Number of valid elements in the |buttons| array.
      */
     uint32_t buttons_length;
 
     /**
      * Normalized values for the buttons, indices valid up to |buttons_length|
      * - 1. Button values range from 0..1, and are in order of importance.
      */
+    [version = 1.0]
     float_t[32] buttons;
 
     /**
+     * Normalized values for the buttons, indices valid up to |buttons_length|
+     * - 1. Button values range from 0..1, and are in order of importance.
+     */
+    [version = 1.1]
+    double_t[32] buttons;
+
+    /**
      * Monotonically increasing value that is incremented when the data have
      * been updated.
      */
     double_t timestamp;
 
     /**
      * Identifier for the type of device/manufacturer.
      */
     uint16_t[128] id;
 
     /**
      * Is there a gamepad connected at this index? If this is false, no other
      * data in this structure is valid.
      */
     PP_Bool connected;
 
     /* Padding to make the struct the same size between 64 and 32. */
     char[4] unused_pad_;
 };
 
 /**
  * The data for all gamepads connected to the system.
  */
-[assert_size(1896)]
+[assert_size(2696)]
 struct PP_GamepadsSampleData {
     /**
      * Number of valid elements in the |items| array.
      */
     uint32_t length;
 
     /* Padding to make the struct the same size between 64 and 32. */
     char[4] unused_pad_;
 
     /**
      * Data for an individual gamepad device connected to the system.
      */
     PP_GamepadSampleData[4] items;
 };
 
 /**
  * The <code>PPB_Gamepad</code> interface allows retrieving data from
  * gamepad/joystick devices that are connected to the system.
  */
 [version=1.0, macro="PPB_GAMEPAD_INTERFACE", singleton]

[dmichael (off chromium), 2014/05/14 15:14:04]

This needs a new version (1.1). I'm not certain how the IDL generator will
handle this if you just omit "version=1.0" or change it to "version=1.1"... I
don't know that we've done a change like this where the function signature has
not changed, but a struct parameter *has* changed.

What I think we *want* is to have two versions of PP_GamepadsSampleData:
PP_GamepadsSampleData_1_0 and PP_GamepadsSampleData_1_1, and maybe a
PP_GamepadsSampleData typedef to the 1.1 version.

In our backing implementation, we'll need to know which one the plugin is using,
so the browser can write the correct one in to shared memory
(content/browser/renderer_host/pepper_gamepad_host.*). The proxy also might need
to change to accommodate the new size. Maybe it would be good enough to always
deal with the larger size, and the smaller one will "just work". That code's in
ppapi/proxy/gamepad_resource.*

 interface PPB_Gamepad {
   /**
    * Samples the current state of the available gamepads.
    */
   [always_set_output_parameters]
   void Sample(
       [in] PP_Instance instance,
       [out] PP_GamepadsSampleData data);
 };