Don't trigger HTTPS Previews unless there is a chrome-proxy header

(cherry picked from commit b8b8b0aec3606c7c9d4f1934c70e34b25b621e94)

Bug: 972756
Change-Id: I18e4716e31859f171a29edbfd70a19f86f24c708
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1652422
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#668654}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1658936
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/branch-heads/3809@{#304}
Cr-Branched-From: d82dec1a818f378c464ba307ddd9c92133eac355-refs/heads/master@{#665002}

diff --git a/chrome/browser/previews/previews_content_util.cc b/chrome/browser/previews/previews_content_util.cc
index abdd661..86c4077 100644
--- a/chrome/browser/previews/previews_content_util.cc
+++ b/chrome/browser/previews/previews_content_util.cc

@@ -103,6 +103,11 @@
         PreviewsLitePageNavigationThrottle::IneligibleReason::kCookiesBlocked);
   }
 
+  if (!decider->has_drp_headers()) {
+    ineligible_reasons.push_back(PreviewsLitePageNavigationThrottle::
+                                     IneligibleReason::kInvalidProxyHeaders);
+  }
+
   // Record UMA.
   for (PreviewsLitePageNavigationThrottle::IneligibleReason reason :
        ineligible_reasons) {

diff --git a/chrome/browser/previews/previews_lite_page_browsertest.cc b/chrome/browser/previews/previews_lite_page_browsertest.cc
index 10ab94a..b1e4ad8 100644
--- a/chrome/browser/previews/previews_lite_page_browsertest.cc
+++ b/chrome/browser/previews/previews_lite_page_browsertest.cc

@@ -1065,6 +1065,31 @@
 
 IN_PROC_BROWSER_TEST_P(
     PreviewsLitePageServerBrowserTest,
+    DISABLE_ON_WIN_MAC_CHROMESOS(LitePagePreviewsNoChromeProxyHeader)) {
+  ui_test_utils::NavigateToURL(browser(), HttpsLitePageURL(kSuccess));
+  VerifyPreviewLoaded();
+
+  // Mimic a bad proxy header update.
+  net::HttpRequestHeaders empty;
+  PreviewsService* previews_service =
+      PreviewsServiceFactory::GetForProfile(browser()->profile());
+  PreviewsLitePageDecider* decider =
+      previews_service->previews_lite_page_decider();
+  decider->OnProxyRequestHeadersChanged(empty);
+
+  base::HistogramTester histogram_tester;
+  ui_test_utils::NavigateToURL(browser(), HttpsLitePageURL(kSuccess));
+  VerifyPreviewNotLoaded();
+
+  histogram_tester.ExpectBucketCount(
+      "Previews.ServerLitePage.IneligibleReasons",
+      static_cast<int>(PreviewsLitePageNavigationThrottle::IneligibleReason::
+                           kInvalidProxyHeaders),
+      1);
+}
+
+IN_PROC_BROWSER_TEST_P(
+    PreviewsLitePageServerBrowserTest,
     DISABLE_ON_WIN_MAC_CHROMESOS(CoinFlipHoldbackTriggering)) {
   base::test::ScopedFeatureList scoped_feature_list;
   scoped_feature_list.InitAndEnableFeatureWithParameters(

diff --git a/chrome/browser/previews/previews_lite_page_decider.cc b/chrome/browser/previews/previews_lite_page_decider.cc
index 036d3af6..58012c5 100644
--- a/chrome/browser/previews/previews_lite_page_decider.cc
+++ b/chrome/browser/previews/previews_lite_page_decider.cc

@@ -23,6 +23,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_metrics.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_service.h"
+#include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_params.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/pref_registry/pref_registry_syncable.h"
@@ -138,7 +139,8 @@
       page_id_(base::RandUint64()),
       drp_settings_(nullptr),
       pref_service_(nullptr),
-      host_bypass_blacklist_(std::make_unique<base::DictionaryValue>()) {
+      host_bypass_blacklist_(std::make_unique<base::DictionaryValue>()),
+      drp_headers_valid_(false) {
   if (!browser_context)
     return;
 
@@ -244,6 +246,15 @@
 void PreviewsLitePageDecider::OnProxyRequestHeadersChanged(
     const net::HttpRequestHeaders& headers) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  std::string drp_header;
+  drp_headers_valid_ =
+      headers.GetHeader(data_reduction_proxy::chrome_proxy_header(),
+                        &drp_header) &&
+      (drp_header.find(",s=") != std::string::npos ||
+       drp_header.find(" s=") != std::string::npos ||
+       base::StartsWith(drp_header, "s=", base::CompareCase::SENSITIVE));
+
   // This is done so that successive page ids cannot be used to track users
   // across sessions. These sessions are contained in the chrome-proxy header.
   page_id_ = base::RandUint64();

diff --git a/chrome/browser/previews/previews_lite_page_decider.h b/chrome/browser/previews/previews_lite_page_decider.h
index df594e71..c9c0b18 100644
--- a/chrome/browser/previews/previews_lite_page_decider.h
+++ b/chrome/browser/previews/previews_lite_page_decider.h

@@ -97,12 +97,14 @@
                              base::TimeDelta duration) override;
   bool HostBlacklistedFromBypass(const std::string& host) override;
 
- private:
   // data_reduction_proxy::DataReductionProxySettingsObserver:
   void OnProxyRequestHeadersChanged(
       const net::HttpRequestHeaders& headers) override;
   void OnSettingsInitialized() override;
 
+  bool has_drp_headers() const { return drp_headers_valid_; }
+
+ private:
   // The time after which it is ok to send the server more preview requests.
   base::Optional<base::TimeTicks> retry_at_;
 
@@ -133,6 +135,10 @@
   // after the time value. This is stored persistently in prefs.
   std::unique_ptr<base::DictionaryValue> host_bypass_blacklist_;
 
+  // A bool that tracks if the last call to |OnProxyRequestHeadersChanged| had
+  // what looked like a valid chrome-proxy header.
+  bool drp_headers_valid_;
+
   SEQUENCE_CHECKER(sequence_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(PreviewsLitePageDecider);

diff --git a/chrome/browser/previews/previews_lite_page_navigation_throttle.h b/chrome/browser/previews/previews_lite_page_navigation_throttle.h
index 593d5c43..1c5c5e62 100644
--- a/chrome/browser/previews/previews_lite_page_navigation_throttle.h
+++ b/chrome/browser/previews/previews_lite_page_navigation_throttle.h

@@ -63,7 +63,8 @@
     kECTUnknown_DEPRECATED = 8,
     kExceededMaxNavigationRestarts = 9,
     kPreviewsState_DEPRECATED = 10,
-    kMaxValue = kPreviewsState_DEPRECATED,
+    kInvalidProxyHeaders = 11,
+    kMaxValue = kInvalidProxyHeaders,
   };
 
   // The response type from the previews server. This enum must

diff --git a/tools/metrics/histograms/enums.xml b/tools/metrics/histograms/enums.xml
index 5d3709dc..caf20141 100644
--- a/tools/metrics/histograms/enums.xml
+++ b/tools/metrics/histograms/enums.xml

@@ -47230,6 +47230,7 @@
       label="Exceeded maximum number of navigation restarts or a redirect
              loop was detected"/>
   <int value="10" label="(DEPRECATED IN M74) Disallowed by PreviewsState"/>
+  <int value="11" label="The chrome-proxy header is invalid"/>
 </enum>
 
 <enum name="PreviewsServerLitePageServerResponse">