[Offline Pages] Change prefetch settings text to refer to downloaded pages.

This updates the "Network Prediction" setting text on Android only.

Bug: 701939
Change-Id: I6fa2079204b00ca96aa6c8451afd523b5c3f6763
Reviewed-on: https://chromium-review.googlesource.com/689747Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Justin DeWitt <dewittj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505138}

chrome/android/java/res/xml/privacy_preferences.xml

@@ -29,6 +29,7 @@
     <org.chromium.chrome.browser.preferences.ChromeBaseCheckBoxPreference
         android:key="network_predictions"
         android:title="@string/network_predictions_title"
+        android:summary="@string/network_predictions_summary"
         android:persistent="false" />
     <Preference
         android:key="usage_and_crash_reports"

chrome/android/java/strings/android_chrome_strings.grd

@@ -568,8 +568,11 @@ CHAR-LIMIT guidelines:
       <message name="IDS_NTP_SITES_EXPLORATION_CATEGORY_OTHER_TITLE" desc="In the Sites Explore UI, title of the Unknown category.">
         Other
       </message>
-      <message name="IDS_NETWORK_PREDICTIONS_TITLE" desc="Title for Prefetch page resources.">
-        Use a prediction service to load pages more quickly
+      <message name="IDS_NETWORK_PREDICTIONS_TITLE" desc="Title of a setting in Chrome settings. Followed by a body that describes what pages are downloaded. If setting is turned on, Chrome will download certain pages to the user’s phone automatically for offline reading. “Download” is a verb, imperative. ">
+        Automatically download pages
+      </message>
+      <message name="IDS_NETWORK_PREDICTIONS_SUMMARY" desc="Body text for the “Automatically download pages” setting in Chrome settings. Describes what happens if the setting is turned on. Load pages refers to how quickly website pages load. Offline reading refers to the ability to access the pages without a network connection.">
+        Load pages more quickly and save popular pages for offline reading
       </message>
       <message name="IDS_CONTEXTUAL_SEARCH_TITLE" desc="Name for the Contextual Search feature, which allows users to search for a term in a web page by tapping on it.">
         Touch to Search