Prerender: Disable prerendering when datasaver is on

This CL stops prerendering if the Data Saver is enabled on Android
devices.

Bug: 1350825
Change-Id: I844dac1369acde7775c1b426f296ce36d09202c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3820184
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Yoshiki Tanioka <tanioka@google.com>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Lingqi Chi <lingqi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1034948}

content/browser/devtools/protocol/page_handler.cc

@@ -1410,6 +1410,8 @@ Page::PrerenderFinalStatus PrerenderFinalStatusToProtocol(
       return Page::PrerenderFinalStatusEnum::CrossOriginNavigation;
     case PrerenderHost::FinalStatus::kCrossOriginRedirect:
       return Page::PrerenderFinalStatusEnum::CrossOriginRedirect;
+    case PrerenderHost::FinalStatus::kDataSaverEnabled:
+      return Page::PrerenderFinalStatusEnum::DataSaverEnabled;
     case PrerenderHost::FinalStatus::kDestroyed:
       return Page::PrerenderFinalStatusEnum::Destroyed;
     case PrerenderHost::FinalStatus::kDidFailLoad:

content/browser/preloading/prerender/prerender_browsertest.cc

@@ -4571,28 +4571,24 @@ class ScopedDataSaverTestContentBrowserClient
   raw_ptr<ContentBrowserClient> old_client;
 };
 
-// Tests that the data saver doesn't prevent image load in a prerendered page.
+// Tests that prerender doesn't run when Data Saver mode is enabled.
 IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, DataSaver) {
   const GURL kInitialUrl = GetUrl("/empty.html");
-  const GURL kPrerenderingUrl = GetUrl("/prerender/image.html");
-  const GURL kImageUrl = GetUrl("/blank.jpg");
+  const GURL kPrerenderingUrl = GetUrl("/empty.html?prerender");
 
   // Enable data saver.
   ScopedDataSaverTestContentBrowserClient scoped_content_browser_client;
   shell()->web_contents()->OnWebPreferencesChanged();
 
-  // Navigate to an initial page.
+  test::PrerenderHostRegistryObserver observer(*web_contents_impl());
   ASSERT_TRUE(NavigateToURL(shell(), kInitialUrl));
-  ASSERT_EQ(shell()->web_contents()->GetLastCommittedURL(), kInitialUrl);
-
-  // Start prerendering `kPrerenderingUrl`.
-  ASSERT_EQ(GetRequestCount(kPrerenderingUrl), 0);
-  AddPrerender(kPrerenderingUrl);
-  EXPECT_EQ(GetRequestCount(kPrerenderingUrl), 1);
+  AddPrerenderAsync(kPrerenderingUrl);
+  observer.WaitForTrigger(kPrerenderingUrl);
 
-  // A request for the image in the prerendered page shouldn't be prevented by
-  // the data saver.
-  EXPECT_EQ(GetRequestCount(kImageUrl), 1);
+  // Prerendering should fail.
+  ExpectFinalStatusForSpeculationRule(
+      PrerenderHost::FinalStatus::kDataSaverEnabled);
+  EXPECT_FALSE(HasHostForUrl(kPrerenderingUrl));
 }
 
 // Tests that loading=lazy doesn't prevent image load in a prerendered page.

content/browser/preloading/prerender/prerender_host.cc

@@ -681,6 +681,7 @@ void PrerenderHost::SetFailureReason(FinalStatus status) {
     case FinalStatus::kEmbedderTriggeredAndCrossOriginRedirected:
     case FinalStatus::kMemoryLimitExceeded:
     case FinalStatus::kFailToGetMemoryUsage:
+    case FinalStatus::kDataSaverEnabled:
       attempt_->SetFailureReason(ToPreloadingFailureReason(status));
       return;
   }

content/browser/preloading/prerender/prerender_host.h

@@ -95,7 +95,8 @@ class CONTENT_EXPORT PrerenderHost : public WebContentsObserver {
     kEmbedderTriggeredAndDestroyed = 35,
     kMemoryLimitExceeded = 36,
     kFailToGetMemoryUsage = 37,
-    kMaxValue = kFailToGetMemoryUsage,
+    kDataSaverEnabled = 38,
+    kMaxValue = kDataSaverEnabled,
   };
 
   PrerenderHost(const PrerenderAttributes& attributes,

content/browser/preloading/prerender/prerender_host_registry.cc

@@ -23,6 +23,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_delegate.h"
+#include "content/public/common/content_client.h"
 #include "services/resource_coordinator/public/cpp/memory_instrumentation/memory_instrumentation.h"
 #include "third_party/blink/public/common/features.h"
 
@@ -124,6 +125,17 @@ int PrerenderHostRegistry::CreateAndStartHost(
       return RenderFrameHost::kNoFrameTreeNodeId;
     }
 
+    // Don't prerender when the Data Saver setting is enabled.
+    if (GetContentClient()->browser()->IsDataSaverEnabled(
+            web_contents.GetBrowserContext())) {
+      RecordPrerenderHostFinalStatus(
+          PrerenderHost::FinalStatus::kDataSaverEnabled, attributes,
+          ukm::kInvalidSourceId);
+      if (attempt)
+        attempt->SetEligibility(PreloadingEligibility::kDataSaverEnabled);
+      return RenderFrameHost::kNoFrameTreeNodeId;
+    }
+
     // TODO(crbug.com/1176054): Support cross-origin prerendering.
     // The initiator origin is nullopt when prerendering is initiated by the
     // browser (not by a renderer using Speculation Rules API). In that case,

content/browser/preloading/prerender/prerender_internals_handler_impl.cc

@@ -82,6 +82,8 @@ const char* FinalStatusToString(PrerenderHost::FinalStatus final_status) {
       return "MemoryLimitExceeded";
     case PrerenderHost::FinalStatus::kFailToGetMemoryUsage:
       return "FailToGetMemoryUsage";
+    case PrerenderHost::FinalStatus::kDataSaverEnabled:
+      return "DataSaverEnabled";
   }
   NOTREACHED();
   return "";

content/public/browser/preloading.h

@@ -107,6 +107,9 @@ enum class PreloadingEligibility {
   // Preloading was ineligible as running JavaScript was disabled for the URL.
   kJavascriptDisabled = 6,
 
+  // Preloading was ineligible because the Data Saver setting was enabled.
+  kDataSaverEnabled = 7,
+
   // TODO(crbug.com/1309934): Add more specific ineligibility reasons subject to
   // each preloading operation
   // This constant is used to define the value from which embedders can add more

third_party/blink/public/devtools_protocol/browser_protocol.pdl

@@ -8464,6 +8464,7 @@ domain Page
       # Prerenders can be cancelled when Chrome uses excessive memory. This is
       # recorded when it fails to get the memory usage.
       FailToGetMemoryUsage
+      DataSaverEnabled
 
   # Fired when a prerender attempt is completed.
   experimental event prerenderAttemptCompleted

tools/metrics/histograms/enums.xml

@@ -78940,6 +78940,7 @@ Called by update_net_trust_anchors.py.-->
   <int value="35" label="kEmbedderTriggeredAndDestroyed"/>
   <int value="36" label="kMemoryLimitExceeded"/>
   <int value="37" label="kFailToGetMemoryUsage"/>
+  <int value="38" label="kDataSaverEnabled"/>
 </enum>
 
 <enum name="PrerenderHoverEvent">