Blacklist media URLs via variations

Prevents navigations to media URLs (like an mp4 or jpg) from triggering
HTTPS Server Previews. This blacklist is a comma separated string that
is controlled via field trial.

Bug: 864637
Change-Id: Iff545d975c8c17aa433a95f57d8a01d86cf73279
Reviewed-on: https://chromium-review.googlesource.com/1187200Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585598}

chrome/browser/previews/previews_browsertest.cc

@@ -80,18 +80,21 @@ class PreviewsBrowserTest : public InProcessBrowserTest {
     // Set up https server with resource monitor.
     https_server_.reset(
         new net::EmbeddedTestServer(net::EmbeddedTestServer::TYPE_HTTPS));
-    https_server_->ServeFilesFromSourceDirectory("chrome/test/data/previews");
+    https_server_->ServeFilesFromSourceDirectory("chrome/test/data");
     https_server_->RegisterRequestMonitor(base::BindRepeating(
         &PreviewsBrowserTest::MonitorResourceRequest, base::Unretained(this)));
     ASSERT_TRUE(https_server_->Start());
 
-    https_url_ = https_server_->GetURL("/noscript_test.html");
+    https_url_ = https_server_->GetURL("/previews/noscript_test.html");
     ASSERT_TRUE(https_url_.SchemeIs(url::kHttpsScheme));
 
-    https_no_transform_url_ =
-        https_server_->GetURL("/noscript_test_with_no_transform_header.html");
+    https_no_transform_url_ = https_server_->GetURL(
+        "/previews/noscript_test_with_no_transform_header.html");
     ASSERT_TRUE(https_no_transform_url_.SchemeIs(url::kHttpsScheme));
 
+    https_media_url_ = https_server_->GetURL("/image_decoding/droids.jpg");
+    ASSERT_TRUE(https_media_url_.SchemeIs(url::kHttpsScheme));
+
     // Set up http server with resource monitor and redirect handler.
     http_server_.reset(
         new net::EmbeddedTestServer(net::EmbeddedTestServer::TYPE_HTTP));
@@ -124,6 +127,7 @@ class PreviewsBrowserTest : public InProcessBrowserTest {
 
   const GURL& https_url() const { return https_url_; }
   const GURL& https_no_transform_url() const { return https_no_transform_url_; }
+  const GURL& https_media_url() const { return https_media_url_; }
   const GURL& http_url() const { return http_url_; }
   const GURL& redirect_url() const { return redirect_url_; }
   const GURL& subframe_url() const { return subframe_url_; }
@@ -159,6 +163,7 @@ class PreviewsBrowserTest : public InProcessBrowserTest {
   std::unique_ptr<net::EmbeddedTestServer> http_server_;
   GURL https_url_;
   GURL https_no_transform_url_;
+  GURL https_media_url_;
   GURL http_url_;
   GURL redirect_url_;
   GURL subframe_url_;
@@ -380,7 +385,8 @@ class PreviewsLitePageServerBrowserTest : public PreviewsBrowserTest {
       scoped_refptr<base::FieldTrial> trial =
           base::FieldTrialList::CreateFieldTrial("TrialName1", "GroupName1");
       std::map<std::string, std::string> feature_parameters = {
-          {"previews_host", previews_server().spec()}};
+          {"previews_host", previews_server().spec()},
+          {"blacklisted_path_suffixes", ".mp4,.jpg"}};
       base::FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
           "TrialName1", "GroupName1", feature_parameters);
 
@@ -523,6 +529,10 @@ IN_PROC_BROWSER_TEST_F(PreviewsLitePageServerBrowserTest,
   ui_test_utils::NavigateToURL(browser(), https_lite_page_url(200));
   VerifyPreviewLoaded();
 
+  // Verify the preview is not triggered when loading a media resource.
+  ui_test_utils::NavigateToURL(browser(), https_media_url());
+  VerifyPreviewNotLoaded();
+
   // Verify the preview is not triggered for POST navigations.
   std::string post_data = "helloworld";
   NavigateParams params(browser(), https_url(), ui::PAGE_TRANSITION_LINK);

chrome/browser/previews/previews_lite_page_navigation_throttle.cc

@@ -85,7 +85,8 @@ PreviewsLitePageNavigationThrottle::~PreviewsLitePageNavigationThrottle() =
     default;
 
 bool PreviewsLitePageNavigationThrottle::IsEligibleForPreview() const {
-  if (!navigation_handle()->GetURL().SchemeIs(url::kHttpsScheme))
+  const GURL& url = navigation_handle()->GetURL();
+  if (!url.SchemeIs(url::kHttpsScheme))
     return false;
 
   if (navigation_handle()->IsPost())
@@ -97,9 +98,18 @@ bool PreviewsLitePageNavigationThrottle::IsEligibleForPreview() const {
   if (manager_->IsServerUnavailable())
     return false;
 
-  if (IsPreviewsDomain(navigation_handle()->GetURL()))
+  if (IsPreviewsDomain(url))
     return false;
 
+  std::vector<std::string> blacklisted_path_suffixes =
+      previews::params::LitePagePreviewsBlacklistedPathSuffixes();
+  for (std::string suffix : blacklisted_path_suffixes) {
+    if (base::EndsWith(url.path(), suffix,
+                       base::CompareCase::INSENSITIVE_ASCII)) {
+      return false;
+    }
+  }
+
   return true;
 }
 

components/previews/core/previews_experiments.cc

@@ -135,6 +135,15 @@ base::TimeDelta LitePagePreviewsSingleBypassDuration() {
       60 * 5));
 }
 
+std::vector<std::string> LitePagePreviewsBlacklistedPathSuffixes() {
+  const std::string csv = base::GetFieldTrialParamValueByFeature(
+      features::kLitePageServerPreviews, "blacklisted_path_suffixes");
+  if (csv == "")
+    return {};
+  return base::SplitString(csv, ",", base::TRIM_WHITESPACE,
+                           base::SPLIT_WANT_NONEMPTY);
+}
+
 int PreviewServerLoadshedMaxSeconds() {
   return base::GetFieldTrialParamByFeatureAsInt(
       features::kLitePageServerPreviews, "loadshed_max_seconds",

components/previews/core/previews_experiments.h

@@ -95,6 +95,10 @@ GURL GetLitePagePreviewsDomainURL();
 // The duration of a single bypass for Lite Page Server Previews.
 base::TimeDelta LitePagePreviewsSingleBypassDuration();
 
+// A list of all path suffixes to blacklist from Lite Page Server Previews.
+// Primarily used to prohibit URLs that look like media requests.
+std::vector<std::string> LitePagePreviewsBlacklistedPathSuffixes();
+
 // The maximum number of seconds to loadshed the Previews server for.
 int PreviewServerLoadshedMaxSeconds();