[Android] Upstream the WebView find-in-page API implementation.

android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h

Index: android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h
diff --git a/android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h b/android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h
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index 0000000000000000000000000000000000000000..af2154b6437b6a976972604953818c8e9717425c
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+++ b/android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ANDROID_WEBVIEW_BROWSER_SCOPED_ALLOW_WAIT_FOR_LEGACY_WEB_VIEW_API_H
+#define ANDROID_WEBVIEW_BROWSER_SCOPED_ALLOW_WAIT_FOR_LEGACY_WEB_VIEW_API_H
+
+#include "base/threading/thread_restrictions.h"
+
+// This class is only available when building the chromium back-end for android
+// webview: it is required where API backward compatibility demands that the UI
+// thread must block waiting on other threads e.g. to obtain a synchronous
+// return value. Long term, asynchronous overloads of all such methods will be
+// added in the public API, and and no new uses of this will be allowed.
+class ScopedAllowWaitForLegacyWebViewApi {
+ private:
+  base::ThreadRestrictions::ScopedAllowWait wait;
+};
+
+#endif  // ANDROID_WEBVIEW_BROWSER_SCOPED_ALLOW_WAIT_FOR_LEGACY_WEB_VIEW_API_H