Hold messages in message port service when a message port is

android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java

Index: android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java b/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
index 4229cf5d576c94279ec72a026a900eab81885787..626d427473197bddf14472a170c098cfdbcc7817 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwMessagePortService.java
@@ -115,6 +115,12 @@ public class AwMessagePortService {
         return new MessagePort[]{new MessagePort(this), new MessagePort(this)};
     }
 
+    // Called on UI thread.
+    public void releaseMessages(int portId) {
+        if (mNativeMessagePortService == 0) return;
+        nativeReleaseMessages(mNativeMessagePortService, portId);
+    }
+
     private MessagePort addPort(MessagePort m, int portId) {
         if (mPortStorage.get(portId) != null) {
             throw new IllegalStateException("Port already exists");
@@ -152,4 +158,6 @@ public class AwMessagePortService {
             int senderId, String message, int[] portIds);
     private native void nativeClosePort(long nativeAwMessagePortServiceImpl,
             int messagePortId);
+    private native void nativeReleaseMessages(long nativeAwMessagePortServiceImpl,
+            int messagePortId);
 }