Fix BrowserActionContainer chevron visibility regression

https://codereview.chromium.org/476873002 introduced a regression where
shrinking the size of the extensions toolbar to 0 would not show the chevron
anymore.  Fix the regression, and add a test so it doesn't happen again.

BUG=407134

Review URL: https://codereview.chromium.org/492503004

Cr-Commit-Position: refs/heads/master@{#291754}

chrome/browser/ui/views/toolbar/browser_actions_container.cc

@@ -318,7 +318,10 @@ void BrowserActionsContainer::RemoveObserver(
 }
 
 gfx::Size BrowserActionsContainer::GetPreferredSize() const {
-  size_t icon_count = GetIconCount();
+  // Note: We can't use GetIconCount() for the main bar, since we may also
+  // have to include items that are in the chevron's overflow.
+  size_t icon_count =
+      in_overflow_mode() ? GetIconCount() : browser_action_views_.size();
 
   // If there are no actions to show, or we are in overflow mode and the main
   // container is already showing them all, then no further work is required.

chrome/browser/ui/views/toolbar/browser_actions_container_browsertest.cc

@@ -217,6 +217,18 @@ IN_PROC_BROWSER_TEST_F(BrowserActionsContainerTest, Visibility) {
   EXPECT_EQ(3, browser_actions_bar()->NumberOfBrowserActions());
   EXPECT_EQ(3, browser_actions_bar()->VisibleBrowserActions());
   EXPECT_EQ(idA, browser_actions_bar()->GetExtensionId(0));
+
+  // Shrink the browser actions bar to zero visible icons.
+  // No icons should be visible, but we *should* show the chevron and have a
+  // non-empty size.
+  browser_actions_bar()->SetIconVisibilityCount(0);
+  EXPECT_EQ(0, browser_actions_bar()->VisibleBrowserActions());
+  BrowserActionsContainer* container =
+      BrowserView::GetBrowserViewForBrowser(browser())
+          ->toolbar()->browser_actions();
+  ASSERT_TRUE(container->chevron());
+  EXPECT_TRUE(container->chevron()->visible());
+  EXPECT_FALSE(container->GetPreferredSize().IsEmpty());
 }
 
 IN_PROC_BROWSER_TEST_F(BrowserActionsContainerTest, ForceHide) {