Add power monitoring to the Cast VideoToolbox encoder.

media/cast/sender/h264_vt_encoder.cc

Index: media/cast/sender/h264_vt_encoder.cc
diff --git a/media/cast/sender/h264_vt_encoder.cc b/media/cast/sender/h264_vt_encoder.cc
index 47e6c8fba7d55ab970b3da21812aa6e73cdeba04..fae7c0d40c9ba4773caf3fb323d4a47ae46317c0 100644
--- a/media/cast/sender/h264_vt_encoder.cc
+++ b/media/cast/sender/h264_vt_encoder.cc
@@ -13,6 +13,7 @@
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/power_monitor/power_monitor.h"
 #include "base/synchronization/lock.h"
 #include "media/base/mac/corevideo_glue.h"
 #include "media/base/mac/video_frame_mac.h"
@@ -300,6 +301,38 @@ class H264VideoToolboxEncoder::VideoFrameFactoryImpl::Proxy
   DISALLOW_COPY_AND_ASSIGN(Proxy);
 };
 
+H264VideoToolboxEncoder::PowerObserver::PowerObserver(
+    H264VideoToolboxEncoder* encoder)
+    : encoder_(encoder) {
+  DCHECK(encoder_);
+  auto power_monitor = base::PowerMonitor::Get();
+  if (!power_monitor) {
+    DLOG(WARNING) << "No power monitor. Encoder may fail if power state change "
+                     "goes undetected.";
+    return;
+  }
+  power_monitor->AddObserver(this);
+  VLOG(1) << "Registered for power state changes.";
+}
+
+H264VideoToolboxEncoder::PowerObserver::~PowerObserver() {
+  auto power_monitor = base::PowerMonitor::Get();
+  if (power_monitor)
+    power_monitor->RemoveObserver(this);
+}
+
+void H264VideoToolboxEncoder::PowerObserver::OnSuspend() {
+  VLOG(1)
+      << "OnSuspend: Emitting all frames and destroying compression session.";
+  encoder_->EmitFrames();
+  encoder_->DestroyCompressionSession();
+}
+
+void H264VideoToolboxEncoder::PowerObserver::OnResume() {
+  VLOG(1) << "OnResume: Resetting compression session.";
+  encoder_->ResetCompressionSession();
+}
+
 // static
 bool H264VideoToolboxEncoder::IsSupported(
     const VideoSenderConfig& video_config) {
@@ -314,6 +347,7 @@ H264VideoToolboxEncoder::H264VideoToolboxEncoder(
       videotoolbox_glue_(VideoToolboxGlue::Get()),
       video_config_(video_config),
       status_change_cb_(status_change_cb),
+      power_observer_(this),
       last_frame_id_(kStartFrameId),
       encode_next_frame_as_keyframe_(false),
       weak_factory_(this) {