[Chromecast] Add volume step interval getter to AvSettings.

chromecast/public/avsettings.h

 // Copyright 2015 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 CHROMECAST_PUBLIC_AVSETTINGS_H_
 #define CHROMECAST_PUBLIC_AVSETTINGS_H_
 
 #include <stdint.h>
 
 #include "output_restrictions.h"
@@ skipping 85 matching lines @@
     // This event should be fired whenever the active output restrictions on the
     // device outputs change. On this event, GetOutputRestrictions() will be
     // called on the thread where Initialize() was called.
     OUTPUT_RESTRICTIONS_CHANGED = 4,
 
     // This event shall be fired whenever the type of volume control provided
     // by the device is changed, for e.g., when the device is connected or
     // disconnected to HDMI sinks
     AUDIO_VOLUME_CONTROL_TYPE_CHANGED = 5,
 
+    // This event shall be fired whenever the volume step interval provided
+    // by the device is changed, for e.g. when connecting to an AVR setup
+    // where step interval should be 1%.
+    AUDIO_VOLUME_STEP_INTERVAL_CHANGED = 6,

[gfhuang, 2016/01/20 22:48:22]

I think you should just give up ordering and use next one, i.e. 7

it's general good practice not to change existing enums

+
     // This event shall be fired whenever wake-on-cast status is changed by
     // platform.
-    WAKE_ON_CAST_CHANGED = 6,
+    WAKE_ON_CAST_CHANGED = 7,
 
     // This event should be fired when the device is connected to HDMI sinks.
     HDMI_CONNECTED = 100,
 
     // This event should be fired when the device is disconnected to HDMI sinks.
     HDMI_DISCONNECTED = 101,
   };
 
   // Delegate to inform the caller events. As a subclass of TaskRunner,
   // AvSettings implementation can post tasks to the thread where Initialize()
@@ skipping 51 matching lines @@
   // Returns true if successful.
   virtual bool KeepSystemAwake(int time_ms) = 0;
 
   // Returns the type of volume control, i.e. MASTER_VOLUME, FIXED_VOLUME or
   // ATTENUATION_VOLUME. For example, normal TVs, devices of CEC audio
   // controls, and audio devices are master volume systems. The counter
   // examples are Chromecast (which doesn't do CEC audio controls) and
   // Nexus Player which is fixed volume.
   virtual AudioVolumeControlType GetAudioVolumeControlType() = 0;
 
+  // Retrieves the volume step interval as percentage in range [0.0, 1.0] that
+  // specifies how much volume to change per step. Returns true if a valid
+  // interval is specified by platform; returns false if interval should defer
+  // to default values.
+  //
+  // Current default volume step intervals per control type are as follows:
+  //  - MASTER_VOLUME (5%)

[gfhuang, 2016/01/20 22:48:22]

"5%" -> "5%, i.e. 0.05" to make it more clear in the range of [0.0, 1.0]

+  //  - ATTENUATION_VOLUME (2%)
+  //  - FIXED_VOLUME (1%)
+  //  - UNKNOWN_VOLUME (1%)
+  virtual bool GetAudioVolumeStepInterval(float* step_inteval) = 0;
+
   // Returns the current volume level, which must be from 0.0 (inclusive) to
   // 1.0 (inclusive).
   virtual float GetAudioVolume() = 0;
 
   // Sets new volume level of the device (or HDMI sinks). |level| is from 0.0
   // (inclusive) to 1.0 (inclusive).
   // If successful and the level has changed, it must return true and fire
   // AUDIO_VOLUME_CHANGED.
   virtual bool SetAudioVolume(float level) = 0;
 
@@ skipping 33 matching lines @@
   virtual WakeOnCastStatus GetWakeOnCastStatus() = 0;
 
   // Enables/Disables Wake-On-Cast status.
   // Returns false if failed or not supported.
   virtual bool EnableWakeOnCast(bool enabled) = 0;
 };
 
 }  // namespace chromecast
 
 #endif  // CHROMECAST_PUBLIC_AVSETTINGS_H_