Synchronize native adapter access in CronetUrlRequestContext

components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java

Index: components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
diff --git a/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java b/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
index 5d5dc481e110f7bd4727da14789c41f83e5f27e7..f63a5ca8e221e73c0f70b014d580a4b2c6874c75 100644
--- a/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
+++ b/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
@@ -79,10 +79,12 @@ class CronetUrlRequestContext extends CronetEngine {
     public CronetUrlRequestContext(CronetEngine.Builder builder) {
         CronetLibraryLoader.ensureInitialized(builder.getContext(), builder);
         nativeSetMinLogLevel(getLoggingLevel());
-        mUrlRequestContextAdapter = nativeCreateRequestContextAdapter(
-                createNativeUrlRequestContextConfig(builder.getContext(), builder));
-        if (mUrlRequestContextAdapter == 0) {
-            throw new NullPointerException("Context Adapter creation failed.");
+        synchronized (mLock) {
+            mUrlRequestContextAdapter = nativeCreateRequestContextAdapter(
+                    createNativeUrlRequestContextConfig(builder.getContext(), builder));
+            if (mUrlRequestContextAdapter == 0) {
+                throw new NullPointerException("Context Adapter creation failed.");
+            }
         }
 
         // Init native Chromium URLRequestContext on main UI thread.