Don't intercept Flash navigations when the current page is the Flash download page.

Currently, with HBD, if you navigate to https://get.adobe.com/flashplayer and
click "Download", it will trigger the Run Flash prompt. We should ignore
navigations if the source URL is the Flash download page itself.

BUG=656062

Review-Url: https://codereview.chromium.org/2435933002
Cr-Commit-Position: refs/heads/master@{#427005}

chrome/browser/plugins/flash_download_interception.cc

@@ -31,9 +31,13 @@ namespace {
 
 const char kWwwPrefix[] = "www.";
 
-// URLs that will be intercepted with any www. prefix pruned.
+// The URL of the page where Flash can be downloaded.
+const char kFlashDownloadURL[] = "get.adobe.com/flash";
+
+// URLs that will be intercepted with any www. prefix pruned. These should all
+// redirect to |kFlashDownloadURL|.
 const char* kFlashDownloadURLs[] = {
-    "get.adobe.com/flash", "macromedia.com/go/getflashplayer",
+    kFlashDownloadURL, "macromedia.com/go/getflashplayer",
     "adobe.com/go/getflashplayer", "adobe.com/go/gntray_dl_getflashplayer"};
 
 void DoNothing(blink::mojom::PermissionStatus result) {}
@@ -89,6 +93,13 @@ bool FlashDownloadInterception::ShouldStopFlashDownloadAction(
   if (!has_user_gesture)
     return false;
 
+  // If the navigation source is already the Flash download page, don't
+  // intercept the download. The user may be trying to download Flash.
+  if (base::StartsWith(source_url.GetContent(), kFlashDownloadURL,
+                       base::CompareCase::INSENSITIVE_ASCII)) {
+    return false;
+  }
+
   std::string target_url_str = target_url.GetContent();
   // Ignore www. if it's at the start of the URL.
   if (base::StartsWith(target_url_str, kWwwPrefix,

chrome/browser/plugins/flash_download_interception_unittest.cc

@@ -73,6 +73,11 @@ TEST_F(FlashDownloadInterceptionTest, DownloadUrlVariations) {
   EXPECT_FALSE(FlashDownloadInterception::ShouldStopFlashDownloadAction(
       host_content_settings_map(), GURL("http://source-page.com"),
       GURL("http://ww.macromedia.com/go/getflashplayer"), true));
+
+  // Don't intercept navigations occurring on the flash download page.
+  EXPECT_FALSE(FlashDownloadInterception::ShouldStopFlashDownloadAction(
+      host_content_settings_map(), GURL("https://get.adobe.com/flashplayer/"),
+      GURL("https://get.adobe.com/flashplayer/"), true));
 }
 
 TEST_F(FlashDownloadInterceptionTest, NavigationThrottleCancelsNavigation) {