Add performance tracing event to VideoCaptureDeviceAndroid::OnFrameAvailable

media/video/capture/android/video_capture_device_android.cc

 // Copyright (c) 2013 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.
 
 #include "media/video/capture/android/video_capture_device_android.h"
 
 #include <string>
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
+#include "base/debug/trace_event.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "jni/VideoCapture_jni.h"
 #include "media/base/video_util.h"
 
 using base::android::AttachCurrentThread;
 using base::android::CheckException;
 using base::android::GetClass;
 using base::android::MethodID;
 using base::android::JavaRef;
@@ skipping 167 matching lines @@
 
   Java_VideoCapture_deallocate(env, j_capture_.obj());
 }
 
 void VideoCaptureDeviceAndroid::OnFrameAvailable(
     JNIEnv* env,
     jobject obj,
     jbyteArray data,
     jint length,
     jint rotation) {
+  TRACE_EVENT0("video", "VideoCaptureDeviceAndroid::OnFrameAvailable");

[tommi (sloooow) - chröme, 2013/12/18 14:01:33]

Since Android is very sensitive to performance I have to ask... is there a
performance impact of doing this?
Will we change the outcome by measuring it?

[mcasas, 2013/12/18 14:32:36]

Well, nothing comes for free. From the docs:

"
Trace macros are very low overhead. When tracing is 
not turned on, trace macros cost at most a few dozen
clocks. When running, trace macros cost a few thousand 
clocks at most. Arguments to the trace macro are 
evaluated only when tracing is on --- if tracing is 
off, the value of the arguments dont get computed.
"

Consider wrapping around a #if !defined(NDEBUG) ?

[tommi (sloooow) - chröme, 2013/12/18 15:14:33]

That's good enough for me.  I know how this is implemented on other platforms
but don't know how it's done on Android.  Given the documentation this sounds
like an expected use case.

   DVLOG(3) << "VideoCaptureDeviceAndroid::OnFrameAvailable: length =" << length;
 
   base::AutoLock lock(lock_);
   if (state_ != kCapturing || !client_.get())
     return;
 
   jbyte* buffer = env->GetByteArrayElements(data, NULL);
   if (!buffer) {
     LOG(ERROR) << "VideoCaptureDeviceAndroid::OnFrameAvailable: "
                   "failed to GetByteArrayElements";
@@ skipping 45 matching lines @@
 void VideoCaptureDeviceAndroid::SetErrorState(const std::string& reason) {
   LOG(ERROR) << "VideoCaptureDeviceAndroid::SetErrorState: " << reason;
   {
     base::AutoLock lock(lock_);
     state_ = kError;
   }
   client_->OnError();
 }
 
 }  // namespace media