Ensuring BACK key is getting passed to IMM before handling by Omnibox

Currently IMM is not getting BACK key event correctly, hence the IMM
behavior on back key is not getting executed. Now made it sure that
IMM will get the key event first before reaching to view.

BUG=470001

Review-Url: https://codereview.chromium.org/2108333003
Cr-Commit-Position: refs/heads/master@{#403221}

chrome/android/java/src/org/chromium/chrome/browser/omnibox/UrlBar.java

@@ -23,6 +23,7 @@ import android.view.GestureDetector;
 import android.view.KeyEvent;
 import android.view.MotionEvent;
 import android.view.View;
+import android.view.View.OnKeyListener;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;
 import android.view.accessibility.AccessibilityNodeInfo;
@@ -51,7 +52,7 @@ import java.net.URL;
 /**
  * The URL text entry view for the Omnibox.
  */
-public class UrlBar extends VerticallyFixedEditText {
+public class UrlBar extends VerticallyFixedEditText implements OnKeyListener {
     private static final String TAG = "UrlBar";
 
     // TextView becomes very slow on long strings, so we limit maximum length
@@ -224,6 +225,7 @@ public class UrlBar extends VerticallyFixedEditText {
 
         mAccessibilityManager =
                 (AccessibilityManager) context.getSystemService(Context.ACCESSIBILITY_SERVICE);
+        setOnKeyListener(this);
     }
 
     /**
@@ -507,10 +509,9 @@ public class UrlBar extends VerticallyFixedEditText {
     }
 
     @Override
-    public boolean onKeyPreIme(int keyCode, KeyEvent event) {
+    public boolean onKey(View v, int keyCode, KeyEvent event) {
         if (keyCode == KeyEvent.KEYCODE_BACK) {
-            if (event.getAction() == KeyEvent.ACTION_DOWN
-                    && event.getRepeatCount() == 0) {
+            if (event.getAction() == KeyEvent.ACTION_DOWN && event.getRepeatCount() == 0) {
                 // Tell the framework to start tracking this event.
                 getKeyDispatcherState().startTracking(event, this);
                 return true;
@@ -522,7 +523,7 @@ public class UrlBar extends VerticallyFixedEditText {
                 }
             }
         }
-        return super.onKeyPreIme(keyCode, event);
+        return false;
     }
 
     @Override