Photo Picker Dialog: Make sure Back button fires the Cancel action.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PickerCategoryView.java

Index: chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PickerCategoryView.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PickerCategoryView.java b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PickerCategoryView.java
index 3f7a03c3e54a5769c81591268f8fa3d1851c42b7..24bdc226e65f2ba107dbd0408fd2e8f48bb92f06 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PickerCategoryView.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/PickerCategoryView.java
@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.photo_picker;
 
 import android.app.Activity;
 import android.content.Context;
+import android.content.DialogInterface;
 import android.content.res.Configuration;
 import android.graphics.Bitmap;
 import android.graphics.Rect;
@@ -190,6 +191,13 @@ public class PickerCategoryView extends RelativeLayout
         mDialog = dialog;
         mMultiSelectionAllowed = multiSelectionAllowed;
         mListener = listener;
+
+        mDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
+            @Override
+            public void onCancel(DialogInterface dialog) {
+                mListener.onPickerUserAction(PhotoPickerListener.Action.CANCEL, null);
+            }
+        });
     }
 
     // FileEnumWorkerTask.FilesEnumeratedCallback: