Keep the reference to local private variable.

android_webview/java/src/org/chromium/android_webview/AwPdfExporter.java

Index: android_webview/java/src/org/chromium/android_webview/AwPdfExporter.java
diff --git a/android_webview/java/src/org/chromium/android_webview/AwPdfExporter.java b/android_webview/java/src/org/chromium/android_webview/AwPdfExporter.java
index 97f84fb1e81cbee6f20dc287c69d84e1e3580e19..b22350e90043dd9265390f20e42aa5521e06f97f 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwPdfExporter.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwPdfExporter.java
@@ -33,7 +33,9 @@ public class AwPdfExporter {
     // Maintain a reference to the top level object (i.e. WebView) since in a common
     // use case (offscreen webview) application may expect the framework's print manager
     // to own the Webview (via PrintDocumentAdapter).
-    // NOTE: it looks unused, but please do not remove this reference.
+    // NOTE: it looks unused, but please do not remove this reference. There is also a proguard
+    // configuration to prevent this variable to be optimized away. Any name changes should
+    // be reflected there.
     private ViewGroup mContainerView;
 
     AwPdfExporter(ViewGroup containerView) {