[Chromeshine] Prevent crash when eagerly suspending null tab

This crash can occur if, e.g. there are no new tabs open and DWB
informs us that a site is suspended. This CL also adds a unit
test for this case and two instrumentation tests; one for this case
and one for a related one.

Bug: 1148363
Change-Id: I7fad393bd0369c4650fb7b8c2d8bd3c3cde40bed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535912Reviewed-by: Natalie Chouinard <chouinard@chromium.org>
Commit-Queue: Patrick Noland <pnoland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827018}

chrome/android/java/src/org/chromium/chrome/browser/usage_stats/PageViewObserver.java

@@ -127,7 +127,7 @@ public class PageViewObserver {
 
     /** Notify PageViewObserver that {@code fqdn} was just suspended or un-suspended. */
     public void notifySiteSuspensionChanged(String fqdn, boolean isSuspended) {
-        if (mCurrentTab != null && !mCurrentTab.isInitialized()) return;
+        if (mCurrentTab == null || !mCurrentTab.isInitialized()) return;
         SuspendedTab suspendedTab = SuspendedTab.from(mCurrentTab);
         if (fqdn.equals(mLastFqdn) || fqdn.equals(suspendedTab.getFqdn())) {
             if (checkSuspendedTabState(isSuspended, fqdn)) {

chrome/android/javatests/src/org/chromium/chrome/browser/usage_stats/TabSuspensionTest.java

@@ -334,6 +334,35 @@ public class TabSuspensionTest {
         });
     }
 
+    @Test
+    @MediumTest
+    public void testSuspendNullCurrentTab() {
+        mActivityTestRule.loadUrl(mStartingUrl);
+        ChromeTabUtils.closeAllTabs(InstrumentationRegistry.getInstrumentation(), mActivity);
+
+        doReturn(true).when(mSuspensionTracker).isWebsiteSuspended(STARTING_FQDN);
+        suspendDomain(STARTING_FQDN);
+
+        // We can't use loadUrlInNewTab because the site being suspended will prevent loading from
+        // completing, and loadUrlInNewTab expects loading to succeed.
+        ChromeTabUtils.newTabFromMenu(
+                InstrumentationRegistry.getInstrumentation(), mActivityTestRule.getActivity());
+        Tab tab2 = mActivity.getActivityTab();
+
+        startLoadingUrl(tab2, mStartingUrl);
+        waitForSuspendedTabToShow(tab2, STARTING_FQDN);
+    }
+
+    @Test
+    @MediumTest
+    public void testSuspendUninitializedCurrentTab() {
+        mActivityTestRule.loadUrl(mStartingUrl);
+        TestThreadUtils.runOnUiThreadBlocking(() -> mTab.destroy());
+
+        doReturn(true).when(mSuspensionTracker).isWebsiteSuspended(STARTING_FQDN);
+        suspendDomain(STARTING_FQDN);
+    }
+
     private void startLoadingUrl(Tab tab, String url) {
         TestThreadUtils.runOnUiThreadBlocking(
                 () -> { tab.loadUrl(new LoadUrlParams(url, PageTransition.TYPED)); });

chrome/android/junit/src/org/chromium/chrome/browser/usage_stats/PageViewObserverTest.java

@@ -494,6 +494,15 @@ public final class PageViewObserverTest {
         observer.notifySiteSuspensionChanged(STARTING_FQDN, true);
     }
 
+    @Test
+    public void eagerSuspension_nullTab() {
+        PageViewObserver observer = createPageViewObserver();
+        updateUrl(mTab, STARTING_URL);
+
+        didSelectTab(null, TabSelectionType.FROM_USER);
+        observer.notifySiteSuspensionChanged(STARTING_FQDN, true);
+    }
+
     private PageViewObserver createPageViewObserver() {
         PageViewObserver observer = new PageViewObserver(
                 mActivity, mTabModelSelector, mEventTracker, mTokenTracker, mSuspensionTracker);