Don't leak ContentViewCores via ImeAdapter

content/browser/renderer_host/ime_adapter_android.h

Index: content/browser/renderer_host/ime_adapter_android.h
diff --git a/content/browser/renderer_host/ime_adapter_android.h b/content/browser/renderer_host/ime_adapter_android.h
index a2cd2ecb7b7be33763970792fbcf497a860ee4bc..f990498dc86d1c28c4b7665ff541339b6498f017 100644
--- a/content/browser/renderer_host/ime_adapter_android.h
+++ b/content/browser/renderer_host/ime_adapter_android.h
@@ -7,6 +7,8 @@
 
 #include <jni.h>
 
+#include "base/android/jni_helper.h"
+
 namespace content {
 
 class RenderWidgetHostViewAndroid;
@@ -15,6 +17,8 @@ struct NativeWebKeyboardEvent;
 // This class is in charge of dispatching key events from the java side
 // and forward to renderer along with input method results via
 // corresponding host view.
+// Ownership of these objects remains on the native side (see
+// RenderWidgetHostViewAndroid).
 class ImeAdapterAndroid {
  public:
   explicit ImeAdapterAndroid(RenderWidgetHostViewAndroid* rwhva);
@@ -53,7 +57,7 @@ class ImeAdapterAndroid {
 
  private:
   RenderWidgetHostViewAndroid* rwhva_;
-  jobject java_ime_adapter_;
+  JavaObjectWeakGlobalRef java_ime_adapter_;
 };
 
 bool RegisterImeAdapter(JNIEnv* env);