Android Photo Picker: Cancel outdated requests again.

Somewhere along the way we stopped listening to recycler
events, which breaks the mechanism that invalidates old
(outdated) requests for decoding. This CL reinstates
that.

Bug: 793934, 656015
Change-Id: I0df070c851bb75a1dccd1e7b5854c8846905ceb9
Reviewed-on: https://chromium-review.googlesource.com/827015Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524095}

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

@@ -158,6 +158,7 @@ public class PickerCategoryView extends RelativeLayout
         mRecyclerView.setLayoutManager(mLayoutManager);
         mSpacingDecoration = new GridSpacingItemDecoration(mColumns, mPadding);
         mRecyclerView.addItemDecoration(mSpacingDecoration);
+        mRecyclerView.setRecyclerListener(this);
 
         final long maxMemory = ConversionUtils.bytesToKilobytes(Runtime.getRuntime().maxMemory());
         mCacheSizeLarge = (int) (maxMemory / 2); // 1/2 of the available memory.