Update ToolbarPhone to use incognito profile when called incognito.

This CL update the profile passing to TrackerFactory from ToolbarPhone.
Currently, it is always regular profile, however it is not safe because
of possible data leakage from incognito to regular profile.

Therefore, this CL uses |isIncognito| function at ToolbarLayout class
to get correct profile object(i.e., regular or off-the-record profile).

Bug: 1041781
Change-Id: I12324730ed6183ba7019138e5064b8fd98d1b45e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2074677Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Reviewed-by: Ramin Halavati <rhalavati@chromium.org>
Commit-Queue: Side YILMAZ <sideyilmaz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744980}

chrome/android/java/src/org/chromium/chrome/browser/toolbar/top/ToolbarPhone.java

@@ -542,8 +542,11 @@ public class ToolbarPhone extends ToolbarLayout implements Invalidator.Client, O
             openHomepage();
             if (isNativeLibraryReady()
                     && PartnerBrowserCustomizations.isHomepageProviderAvailableAndEnabled()) {
-                TrackerFactory.getTrackerForProfile(Profile.getLastUsedProfile())
-                        .notifyEvent(EventConstants.PARTNER_HOME_PAGE_BUTTON_PRESSED);
+                Profile profile = isIncognito()
+                        ? Profile.getLastUsedRegularProfile().getOffTheRecordProfile()
+                        : Profile.getLastUsedRegularProfile();
+                TrackerFactory.getTrackerForProfile(profile).notifyEvent(
+                        EventConstants.PARTNER_HOME_PAGE_BUTTON_PRESSED);
             }
         }
     }