[Android WebView] Fix thread unsafety in accessing Java side getters

android_webview/native/aw_settings.cc

 // Copyright (c) 2013 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.
 
 #include "android_webview/native/aw_settings.h"
 
 #include "android_webview/browser/renderer_host/aw_render_view_host_ext.h"
 #include "android_webview/native/aw_contents.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
@@ skipping 170 matching lines @@
 
 // static
 void AwSettings::PopulateFixedPreferences(WebPreferences* web_prefs) {
   web_prefs->shrinks_standalone_images_to_fit = false;
   web_prefs->should_clear_document_background = false;
 }
 
 void AwSettings::PopulateWebPreferences(WebPreferences* web_prefs) {
   JNIEnv* env = base::android::AttachCurrentThread();
   CHECK(env);
+  ScopedJavaLocalRef<jobject> scoped_obj = aw_settings_.get(env);
+  jobject obj = scoped_obj.obj();
+  if (!obj) return;
+  // Grab the lock and call PopulateWebPreferencesLocked.
+  Java_AwSettings_populateWebPreferences(
+      env, obj, reinterpret_cast<jlong>(web_prefs));
+}
 
+void AwSettings::PopulateWebPreferencesLocked(
+    JNIEnv* env, jobject obj, jlong web_prefs_ptr) {
   AwRenderViewHostExt* render_view_host_ext = GetAwRenderViewHostExt();
   if (!render_view_host_ext) return;
 
-  ScopedJavaLocalRef<jobject> scoped_obj = aw_settings_.get(env);
-  jobject obj = scoped_obj.obj();
-  if (!obj) return;
-
+  WebPreferences* web_prefs = reinterpret_cast<WebPreferences*>(web_prefs_ptr);
   PopulateFixedPreferences(web_prefs);
 
   web_prefs->text_autosizing_enabled =
       Java_AwSettings_getTextAutosizingEnabledLocked(env, obj);
 
   int text_size_percent = Java_AwSettings_getTextSizePercentLocked(env, obj);
   if (web_prefs->text_autosizing_enabled) {
     web_prefs->font_scale_factor = text_size_percent / 100.0f;
     web_prefs->force_enable_zoom = text_size_percent >= 130;
     // Use the default zoom factor value when Text Autosizer is turned on.
@@ skipping 125 matching lines @@
 static jstring GetDefaultUserAgent(JNIEnv* env, jclass clazz) {
   return base::android::ConvertUTF8ToJavaString(
       env, content::GetUserAgent(GURL())).Release();
 }
 
 bool RegisterAwSettings(JNIEnv* env) {
   return RegisterNativesImpl(env) >= 0;
 }
 
 }  // namespace android_webview