desktop-paws: Fix crash when middle clicking in scope links with link capturing

This CL fixes middle clicks on links inside a link capturing web app
scope from crashing. These were crashing due to the expectation that
the navigating tab was already attached to a browser window (which
is incorrect during the navigation throttle) causing a nullptr crash.

We should not be link capturing these navigations so this CL checks
for and early exits in these cases.

Bug: 1159666
Change-Id: I9dae80d84a44e8bf2fa9918ece8fee6d19af2ee2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2636009
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Maggie Cai <mxcai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844666}

chrome/browser/apps/intent_helper/apps_navigation_throttle.cc

@@ -187,6 +187,11 @@ AppsNavigationThrottle::CaptureWebAppScopeNavigations(
   }
 
   Browser* browser = chrome::FindBrowserWithWebContents(web_contents);
+  if (!browser) {
+    // This is a middle click open in new tab action; do not capture.
+    return base::nullopt;
+  }
+
   if (web_app::AppBrowserController::IsForWebApp(browser, *app_id)) {
     // Already in the app window; navigation already captured.
     return base::nullopt;

chrome/browser/ui/web_applications/test/web_app_navigation_browsertest.cc

@@ -112,7 +112,8 @@ void WebAppNavigationBrowserTest::ClickLinkWithModifiersAndWaitForURL(
     const GURL& target_url,
     WebAppNavigationBrowserTest::LinkTarget target,
     const std::string& rel,
-    int modifiers) {
+    int modifiers,
+    blink::WebMouseEvent::Button button) {
   auto observer = GetTestNavigationObserver(target_url);
   std::string script = base::StringPrintf(
       "(() => {"
@@ -134,8 +135,7 @@ void WebAppNavigationBrowserTest::ClickLinkWithModifiersAndWaitForURL(
       rel.c_str());
   ASSERT_TRUE(content::ExecuteScript(web_contents, script));
 
-  content::SimulateMouseClick(web_contents, modifiers,
-                              blink::WebMouseEvent::Button::kLeft);
+  content::SimulateMouseClick(web_contents, modifiers, button);
 
   observer->Wait();
 }

chrome/browser/ui/web_applications/test/web_app_navigation_browsertest.h

@@ -61,7 +61,9 @@ class WebAppNavigationBrowserTest : public InProcessBrowserTest {
       const GURL& target_url,
       LinkTarget target,
       const std::string& rel,
-      int modifiers);
+      int modifiers,
+      blink::WebMouseEvent::Button button =
+          blink::WebMouseEvent::Button::kLeft);
 
   // Creates an <a> element, sets its href and target to |link_url| and |target|
   // respectively, adds it to the DOM, and clicks on it. Returns once

chrome/browser/ui/web_applications/web_app_link_capturing_browsertest.cc

@@ -144,9 +144,17 @@ IN_PROC_BROWSER_TEST_F(WebAppTabStripLinkCapturingBrowserTest,
   ExpectTabs(browser(), {out_of_scope_});
   ExpectTabs(app_browser, {in_scope_1_, in_scope_2_, scope_});
 
+  // Middle clicking links should not be captured.
+  ClickLinkWithModifiersAndWaitForURL(
+      browser()->tab_strip_model()->GetActiveWebContents(), scope_, scope_,
+      LinkTarget::SELF, "", blink::WebInputEvent::Modifiers::kNoModifiers,
+      blink::WebMouseEvent::Button::kMiddle);
+  ExpectTabs(browser(), {out_of_scope_, scope_});
+  ExpectTabs(app_browser, {in_scope_1_, in_scope_2_, scope_});
+
   // Out of scope should behave as usual.
   Navigate(browser(), out_of_scope_);
-  ExpectTabs(browser(), {out_of_scope_});
+  ExpectTabs(browser(), {out_of_scope_, scope_});
   ExpectTabs(app_browser, {in_scope_1_, in_scope_2_, scope_});
 }