[Cronet] Make HistogramManager an abstract class to break dependency on native library.

components/cronet/android/cronet_histogram_manager.h

Index: components/cronet/android/cronet_histogram_manager.h
diff --git a/components/cronet/android/cronet_histogram_manager.h b/components/cronet/android/cronet_histogram_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..b560b99f408b75bde0d8b877ba973bbcd844f0a0
--- /dev/null
+++ b/components/cronet/android/cronet_histogram_manager.h
@@ -0,0 +1,16 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.

[xunjieli, 2015/02/06 19:05:01]

nit: 2015?

[mef, 2015/02/06 19:28:55]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_CRONET_ANDROID_CRONET_CRONET_HISTOGRAM_MANAGER_H_

[xunjieli, 2015/02/06 19:05:01]

s/COMPONENTS_CRONET_ANDROID_CRONET_CRONET_HISTOGRAM_MANAGER_H_/COMPONENTS_CRONET_ANDROID_CRONET_HISTOGRAM_MANAGER_H_

too many cronet :)

[mef, 2015/02/06 19:28:55]

Hmm, it means that previously guard didn't match the file path. Done.

+#define COMPONENTS_CRONET_ANDROID_CRONET_CRONET_HISTOGRAM_MANAGER_H_
+
+#include <jni.h>
+
+namespace cronet {
+
+bool CronetHistogramManagerRegisterJni(JNIEnv* env);
+
+}  // namespace cronet
+
+#endif  // COMPONENTS_CRONET_ANDROID_CRONET_CRONET_HISTOGRAM_MANAGER_H_