Don't show the Data Saver promo in incognito mode

BUG=737926

Review-Url: https://codereview.chromium.org/2969843004
Cr-Commit-Position: refs/heads/master@{#485456}

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java

@@ -492,8 +492,10 @@ public class ChromeTabbedActivity
                     && preferenceManager.getPromosSkippedOnFirstStart()) {
                 // Data reduction promo should be temporarily suppressed if the sign in promo is
                 // shown to avoid nagging users too much.
+                TabModel currentModel = mTabModelSelectorImpl.getCurrentModel();
                 if (!SigninPromoUtil.launchSigninPromoIfNeeded(this)) {
-                    if (!DataReductionPromoScreen.launchDataReductionPromo(this)
+                    if (!DataReductionPromoScreen.launchDataReductionPromo(
+                                this, currentModel.isIncognito())
                             && getBottomSheet() != null) {
                         getBottomSheet().showHelpBubbleIfNecessary();
                     }

chrome/android/java/src/org/chromium/chrome/browser/preferences/datareduction/DataReductionPromoScreen.java

@@ -24,10 +24,11 @@ public class DataReductionPromoScreen extends PromoDialog {
      * Launch the data reduction promo, if it needs to be displayed.
      * @return Whether the data reduction promo was displayed.
      */
-    public static boolean launchDataReductionPromo(Activity parentActivity) {
+    public static boolean launchDataReductionPromo(Activity parentActivity, boolean isIncognito) {
         // The promo is displayed if Chrome is launched directly (i.e., not with the intent to
         // navigate to and view a URL on startup), the instance is part of the field trial,
         // and the promo has not been displayed before.
+        if (isIncognito) return false;
         if (!DataReductionPromoUtils.canShowPromos()) return false;
         if (DataReductionPromoUtils.getDisplayedFreOrSecondRunPromo()) return false;
         // Showing the promo dialog in multiwindow mode is broken on Galaxy Note devices: