Fix HandlerLeak lint warning

android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java

Index: android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java
diff --git a/android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java b/android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java
index 1d28526a597de73ef6dfc7c835b0da7b1f81f555..a92a0cf7febd404552202440c397002ca3bc780e 100644
--- a/android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java
+++ b/android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java
@@ -110,6 +110,43 @@ public class WebViewContentsClientAdapter extends AwContentsClient {
 
     private WeakHashMap<AwPermissionRequest, WeakReference<PermissionRequestAdapter>>
             mOngoingPermissionRequests;
+
+    private static class UiThreadHandler extends Handler {
+        private final WeakReference<WebView> mWeakWebView;

[boliu, 2016/08/24 00:36:04]

I... don't think this is safe. It's actually conceivable app isn't holding onto
the webview that created the pop up anymore, then gc could actually release it.
so the whole premise of that warning just doesn't hold

I hate these warnings, either it should be applied universally and break build,
or they should just not be turned on at all

+
+        public UiThreadHandler(WebView webView) {
+            mWeakWebView = new WeakReference<WebView>(webView);
+        }
+
+        @Override
+        public void handleMessage(Message msg) {
+            switch (msg.what) {
+                case NEW_WEBVIEW_CREATED:
+                    if (mWeakWebView.get() == null) {

[boliu, 2016/08/24 00:36:04]

this is not c++ WeakPtr, gc can run at any time, and you need to hold a strong
ref here to make sure it doesn't go away in this method

+                        return;

[Torne, 2016/08/24 15:31:36]

Just returning here would mean that even though the app *did* create a new
WebView and pass it to us from onCreateWindow, the popup will never do anything
and effectively be dead (if the app has managed to drop all strong references to
the parent WebView at that point). This doesn't seem like a desirable outcome.

I think we could only do this safely if we also invented a way to finish opening
the popup successfully with a null parent - I have no idea if that's really
possible..

[boliu, 2016/08/24 16:08:59]

It is. Have the native AwContents of the pop up be owned by the message
probably. That probably gets into a lot of weird corner cases that I'd rather
not think about too much. imo current thing is fine

I will support merging all of our handlers so there is only one. There is
another one for handling webview callbacks in AwContentsClientCallbackHelper

+                    }
+                    WebView.WebViewTransport t = (WebView.WebViewTransport) msg.obj;
+                    WebView newWebView = t.getWebView();
+                    if (newWebView == mWeakWebView.get()) {
+                        throw new IllegalArgumentException(
+                                "Parent WebView cannot host it's own popup window. Please "
+                                + "use WebSettings.setSupportMultipleWindows(false)");
+                    }
+
+                    if (newWebView != null && newWebView.copyBackForwardList().getSize() != 0) {
+                        throw new IllegalArgumentException(
+                                "New WebView for popup window must not have been previously "
+                                + "navigated.");
+                    }
+
+                    WebViewChromium.completeWindowCreation(mWeakWebView.get(), newWebView);
+                    break;
+                default:
+                    throw new IllegalStateException();
+            }
+        }
+    }
+
     /**
      * Adapter constructor.
      *
@@ -130,32 +167,7 @@ public class WebViewContentsClientAdapter extends AwContentsClient {
         mWebViewDelegate = webViewDelegate;
         setWebViewClient(null);
 
-        mUiThreadHandler = new Handler() {
-            @Override
-            public void handleMessage(Message msg) {
-                switch (msg.what) {
-                    case NEW_WEBVIEW_CREATED:
-                        WebView.WebViewTransport t = (WebView.WebViewTransport) msg.obj;
-                        WebView newWebView = t.getWebView();
-                        if (newWebView == mWebView) {
-                            throw new IllegalArgumentException(
-                                    "Parent WebView cannot host it's own popup window. Please "
-                                    + "use WebSettings.setSupportMultipleWindows(false)");
-                        }
-
-                        if (newWebView != null && newWebView.copyBackForwardList().getSize() != 0) {
-                            throw new IllegalArgumentException(
-                                    "New WebView for popup window must not have been previously "
-                                    + "navigated.");
-                        }
-
-                        WebViewChromium.completeWindowCreation(mWebView, newWebView);
-                        break;
-                    default:
-                        throw new IllegalStateException();
-                }
-            }
-        };
+        mUiThreadHandler = new UiThreadHandler(mWebView);
     }
 
     void setWebViewClient(WebViewClient client) {