Use the 30 day history stats for the Data Saver menu item

chrome/android/java/src/org/chromium/chrome/browser/net/spdyproxy/DataReductionProxySettings.java

Index: chrome/android/java/src/org/chromium/chrome/browser/net/spdyproxy/DataReductionProxySettings.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/net/spdyproxy/DataReductionProxySettings.java b/chrome/android/java/src/org/chromium/chrome/browser/net/spdyproxy/DataReductionProxySettings.java
index b65b31733cc6f077f45cc6b5c078f7a7f8eb5465..85c95873d9ff06ed9cdb2c736a322e3c81be8d40 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/net/spdyproxy/DataReductionProxySettings.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/net/spdyproxy/DataReductionProxySettings.java
@@ -204,6 +204,15 @@ public class DataReductionProxySettings {
     }
 
     /**
+     * Returns the content length saved for the number of days shown in the history summary.
+     * @return The content length saved.
+     */
+    public long getContentLengthSavedInHistorySummary() {
+        ContentLengths length = getContentLengths();
+        return Math.max(length.getOriginal() - length.getReceived(), 0);
+    }
+
+    /**
      * Returns the total HTTP content length saved.
      * @return The HTTP content length saved.
      */