[Android] Add proxy for Java-based WebContentsObservers

content/public/android/java/src/org/chromium/content_public/browser/WebContents.java

Index: content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
diff --git a/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java b/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
index 19b00b220e8104733889ba9e9a0ace3bf98a2bce..06bf7ae9cfec15885409f261e4f71675d6f01a9c 100644
--- a/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
+++ b/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
@@ -229,4 +229,18 @@ public interface WebContents {
      * @return Whether the initial empty page has been accessed by a script.
      */
     public boolean hasAccessedInitialDocument();
+
+    /**
+     * Add an observer to the WebContents
+     *
+     * @param observer The observer to add.
+     */
+    void addObserver(WebContentsObserver observer);
+
+    /**
+     * Remove an observer from the WebContents
+     *
+     * @param observer The observer to remove.
+     */
+    void removeObserver(WebContentsObserver observer);
 }