[Feed] destroy image loader after destroy StreamLifecycleManager

Should call image loader's destroy after StreamLifecycleManager::destroy
to avoid race condition, since StreamLifecycleManager may ask image
loader between FeedImageLoader::destroy and
StreamLifecycleManager::destroy.

Change-Id: Ib291ef3716e118c2ba66ffe1e26165f259bcfeaf
Reviewed-on: https://chromium-review.googlesource.com/c/1260008Reviewed-by: Sky Malice <skym@chromium.org>
Reviewed-by: Filip Gorski <fgorski@chromium.org>
Commit-Queue: Filip Gorski <fgorski@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596440}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedNewTabPage.java

@@ -256,8 +256,8 @@ public class FeedNewTabPage extends NewTabPage {
     public void destroy() {
         super.destroy();
         mMediator.destroy();
-        if (mImageLoader != null) mImageLoader.destroy();
         if (mStreamLifecycleManager != null) mStreamLifecycleManager.destroy();
+        if (mImageLoader != null) mImageLoader.destroy();
         mTab.getWindowAndroid().removeContextMenuCloseListener(mContextMenuManager);
     }