Upstream chromium side of modal dialogs for webview.

android_webview/native/aw_web_contents_delegate.cc

Index: android_webview/native/aw_web_contents_delegate.cc
diff --git a/android_webview/native/aw_web_contents_delegate.cc b/android_webview/native/aw_web_contents_delegate.cc
index 73021281e067b482292ed45f64d697085dc0ba96..249ee0f51fadf7a86a6efe8ee61125ec1ed8a394 100644
--- a/android_webview/native/aw_web_contents_delegate.cc
+++ b/android_webview/native/aw_web_contents_delegate.cc
@@ -4,8 +4,14 @@
 
 #include "android_webview/native/aw_web_contents_delegate.h"
 
+#include "base/lazy_instance.h"
+#include "android_webview/native/aw_javascript_dialog_creator.h"
+
 namespace android_webview {
 
+static base::LazyInstance<AwJavaScriptDialogCreator>::Leaky
+    g_javascript_dialog_creator = LAZY_INSTANCE_INITIALIZER;
+
 AwWebContentsDelegate::AwWebContentsDelegate(
     JNIEnv* env,
     jobject obj)
@@ -15,4 +21,9 @@ AwWebContentsDelegate::AwWebContentsDelegate(
 AwWebContentsDelegate::~AwWebContentsDelegate() {
 }
 
+content::JavaScriptDialogCreator*
+AwWebContentsDelegate::GetJavaScriptDialogCreator() {
+  return g_javascript_dialog_creator.Pointer();
+}
+
 }  // namespace android_webview