[Android WebView] Lay the groundwork for a better onReceivedError

android_webview/java/src/org/chromium/android_webview/AwContentsClient.java

Index: android_webview/java/src/org/chromium/android_webview/AwContentsClient.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwContentsClient.java b/android_webview/java/src/org/chromium/android_webview/AwContentsClient.java
index a81b2ed48452b74ec0e6dcd16ee959e6c00b831f..2b5514bc844ca75921e66cae73cac21bd1b39cf1 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContentsClient.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContentsClient.java
@@ -92,6 +92,14 @@ public abstract class AwContentsClient {
         public HashMap<String, String> requestHeaders;
     }
 
+    /**
+     * Parameters for {@link AwContentsClient#onReceivedError} method.
+     */
+    public static class AwWebResourceError {
+        public int errorCode = ErrorCodeConversionHelper.ERROR_UNKNOWN;
+        public String description;
+    }
+
     public abstract void getVisitedHistory(ValueCallback<String[]> callback);
 
     public abstract void doUpdateVisitedHistory(String url, boolean isReload);
@@ -256,7 +264,33 @@ public abstract class AwContentsClient {
 
     public abstract void onPageFinished(String url);
 
-    public abstract void onReceivedError(int errorCode, String description, String failingUrl);
+    public final void onReceivedError(AwWebResourceRequest request, AwWebResourceError error) {
+        // Only one of these callbacks actually reaches out the client code. The first callback
+        // is used on API versions up to and including L, the second on subsequent releases.
+        // Below is the calls diagram:
+        //
+        //                           Old (<= L) glue              Old (<= L) android.webkit API
+        //                             onReceivedError --------->   onReceivedError
+        //  AwContentsClient           onReceivedError2 ->X   /
+        //   abs. onReceivedError                            /
+        //   abs. onReceivedError2                          /
+        //                           New (M+) glue         /      New (M+) android.webkit API
+        //                             onReceivedError    /     ->  onReceviedError <new>
+        //   "->X" = "do nothing"        if (!<M API>) ---     /      if (isMainFrame) -\
+        //                               else ->X             /       else ->X          |
+        //                             onReceivedError2      /                          V
+        //                               if (<M API>) -------       onReceivedError <old>
+        //                               else ->X
+        if (request.isMainFrame) {
+            onReceivedError(error.errorCode, error.description, request.url);
+        }
+        onReceivedError2(request, error);
+    }
+
+    protected abstract void onReceivedError(int errorCode, String description, String failingUrl);
+
+    protected abstract void onReceivedError2(
+            AwWebResourceRequest request, AwWebResourceError error);
 
     // TODO (michaelbai): Remove this method once the same method remove from
     // WebViewContentsClientAdapter.