Updated prefetch tab title to Explore Offline

This CL changes the prefetch tab title text from Articles for You
to Explore Offline.

Bug: None
Change-Id: I52bd208106ed1d73e685690cf0c57896322f50ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2021294
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735738}

chrome/android/java/res_download/layout/download_home_tabs.xml

@@ -25,7 +25,7 @@
             android:id="@+id/prefetch_tab"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:text="@string/ntp_article_suggestions_section_header"/>
+            android:text="@string/download_manager_explore_offline"/>
 
     </android.support.design.widget.TabLayout>
 

chrome/android/javatests/src/org/chromium/chrome/browser/download/home/DownloadActivityV2Test.java

@@ -179,12 +179,12 @@ public class DownloadActivityV2Test extends DummyUiActivityTestCase {
 
         Matcher filesTabMatcher = allOf(
                 withText(equalToIgnoringCase("My Files")), isDescendantOfA(withId(R.id.tabs)));
-        Matcher prefetchTabMatcher = allOf(withText(equalToIgnoringCase("Articles for you")),
+        Matcher prefetchTabMatcher = allOf(withText(equalToIgnoringCase("Explore Offline")),
                 isDescendantOfA(withId(R.id.tabs)));
         onView(filesTabMatcher).check(matches(isDisplayed()));
         onView(prefetchTabMatcher).check(matches(isDisplayed()));
 
-        // Select Articles for you tab, and verify the contents.
+        // Select Explore Offline tab, and verify the contents.
         onView(prefetchTabMatcher).perform(ViewActions.click());
         checkItemsDisplayed(false, false, false, false);
 
@@ -233,7 +233,7 @@ public class DownloadActivityV2Test extends DummyUiActivityTestCase {
         onView(withId(R.id.empty)).check(matches(not(isDisplayed())));
 
         // Go to Prefetch tab. It should be empty.
-        onView(withText(equalToIgnoringCase("Articles for you")))
+        onView(withText(equalToIgnoringCase("Explore Offline")))
                 .check(matches(isDisplayed()))
                 .perform(ViewActions.click());
         onView(withText(containsString("Articles appear here"))).check(matches(isDisplayed()));