[Copy from 1057969] ResourceLoadScheduler: show console messages on reaching the limit

This patch makes the ResourceLoadScheduler show a console message
on receiving a network request when running requests reach to the limit.

This will help users to understand what is happening around the
background tab throttling.

Change from the original change (crrev.com/c/1057969):
- Rebase
- Not to show the message for kStopped (i.e. when a frame is paused)

The latter can be added when the owners of frame-pausing/stopping want
to add that later.

Bug: 837771
Change-Id: Ie17bb21a7172d2108d9cd10c4f3bde8b066b6fdb
Reviewed-on: https://chromium-review.googlesource.com/1136167
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574937}

third_party/blink/renderer/core/loader/base_fetch_context.cc

@@ -86,6 +86,21 @@ const char* GetDestinationFromContext(WebURLRequest::RequestContext context) {
   return "";
 }
 
+MessageSource ConvertLogSourceToMessageSource(FetchContext::LogSource source) {
+  // When LogSource is extended, this switch statement should be modified to
+  // convert LogSource to blink::MessageSource.
+  switch (source) {
+    case FetchContext::kJSSource:
+      return kJSMessageSource;
+    case FetchContext::kSecuritySource:
+      return kSecurityMessageSource;
+    case FetchContext::kOtherSource:
+      return kOtherMessageSource;
+  }
+  NOTREACHED();
+  return kOtherMessageSource;
+}
+
 }  // namespace
 
 void BaseFetchContext::AddAdditionalRequestHeaders(ResourceRequest& request,
@@ -159,19 +174,16 @@ base::Optional<ResourceRequestBlockedReason> BaseFetchContext::CanRequest(
   return blocked_reason;
 }
 
+void BaseFetchContext::AddInfoConsoleMessage(const String& message,
+                                             LogSource source) const {
+  AddConsoleMessage(ConsoleMessage::Create(
+      ConvertLogSourceToMessageSource(source), kInfoMessageLevel, message));
+}
+
 void BaseFetchContext::AddErrorConsoleMessage(const String& message,
                                               LogSource source) const {
-  switch (source) {
-    case kJSSource:
-      AddConsoleMessage(ConsoleMessage::Create(kJSMessageSource,
-                                               kErrorMessageLevel, message));
-      return;
-    case kSecuritySource:
-      AddConsoleMessage(ConsoleMessage::Create(kSecurityMessageSource,
-                                               kErrorMessageLevel, message));
-      return;
-  }
-  NOTREACHED();
+  AddConsoleMessage(ConsoleMessage::Create(
+      ConvertLogSourceToMessageSource(source), kErrorMessageLevel, message));
 }
 
 bool BaseFetchContext::IsAdResource(

third_party/blink/renderer/core/loader/base_fetch_context.h

@@ -58,6 +58,7 @@ class CORE_EXPORT BaseFetchContext : public FetchContext {
   virtual std::unique_ptr<WebSocketHandshakeThrottle>
   CreateWebSocketHandshakeThrottle() = 0;
 
+  void AddInfoConsoleMessage(const String&, LogSource) const override;
   void AddErrorConsoleMessage(const String&, LogSource) const override;
   bool IsAdResource(const KURL&,
                     Resource::Type,

third_party/blink/renderer/platform/loader/fetch/fetch_context.cc

@@ -110,6 +110,8 @@ void FetchContext::DidLoadResource(Resource*) {}
 
 void FetchContext::AddResourceTiming(const ResourceTimingInfo&) {}
 
+void FetchContext::AddInfoConsoleMessage(const String&, LogSource) const {}
+
 void FetchContext::AddErrorConsoleMessage(const String&, LogSource) const {}
 
 void FetchContext::PopulateResourceRequest(

third_party/blink/renderer/platform/loader/fetch/fetch_context.h

@@ -82,14 +82,14 @@ class PLATFORM_EXPORT FetchContext
   // This enum corresponds to blink::MessageSource. We have this not to
   // introduce any dependency to core/.
   //
-  // Currently only kJSMessageSource and kSecurityMessageSource are used, but
-  // not to impress readers that AddConsoleMessage() call from FetchContext()
-  // should always use them, which is not true, we ask users of the
-  // Add.*ConsoleMessage() methods to explicitly specify the MessageSource to
-  // use.
+  // Currently only kJSMessageSource, kSecurityMessageSource and
+  // kOtherMessageSource are used, but not to impress readers that
+  // AddConsoleMessage() call from FetchContext() should always use them,
+  // which is not true, we ask users of the Add.*ConsoleMessage() methods
+  // to explicitly specify the MessageSource to use.
   //
   // Extend this when needed.
-  enum LogSource { kJSSource, kSecuritySource };
+  enum LogSource { kJSSource, kSecuritySource, kOtherSource };
 
   static FetchContext& NullInstance();
 
@@ -210,6 +210,7 @@ class PLATFORM_EXPORT FetchContext
     return false;
   }
 
+  virtual void AddInfoConsoleMessage(const String&, LogSource) const;
   virtual void AddErrorConsoleMessage(const String&, LogSource) const;
 
   virtual const SecurityOrigin* GetSecurityOrigin() const { return nullptr; }

third_party/blink/renderer/platform/loader/fetch/resource_load_scheduler.cc

@@ -469,7 +469,24 @@ void ResourceLoadScheduler::Request(ResourceLoadSchedulerClient* client,
   pending_requests_[option].insert(request_info);
   pending_request_map_.insert(
       *id, new ClientInfo(client, option, priority, intra_priority));
+
+  // Remember the ClientId since MaybeRun() below may destruct the caller
+  // instance and |id| may be inaccessible after the call.
+  ResourceLoadScheduler::ClientId client_id = *id;
   MaybeRun();
+
+  if (IsThrottledState() &&
+      pending_request_map_.find(client_id) != pending_request_map_.end()) {
+    // Note that this doesn't show the message when a frame is stopped (vs.
+    // this DOES when throttled).
+    context_->AddInfoConsoleMessage(
+        "Active resource loading counts reached to a per-frame limit while the "
+        "tab is in background. Network requests will be delayed until a "
+        "previous loading finishes, or the tab is foregrounded. See "
+        "https://www.chromestatus.com/feature/5527160148197376 for more "
+        "details",
+        FetchContext::kOtherSource);
+  }
 }
 
 void ResourceLoadScheduler::SetPriority(ClientId client_id,
@@ -740,4 +757,16 @@ size_t ResourceLoadScheduler::GetOutstandingLimit() const {
   return limit;
 }
 
+bool ResourceLoadScheduler::IsThrottledState() const {
+  switch (frame_scheduler_lifecycle_state_) {
+    case scheduler::SchedulingLifecycleState::kHidden:
+    case scheduler::SchedulingLifecycleState::kThrottled:
+      return true;
+    case scheduler::SchedulingLifecycleState::kStopped:
+    case scheduler::SchedulingLifecycleState::kNotThrottled:
+      break;
+  }
+  return false;
+}
+
 }  // namespace blink

third_party/blink/renderer/platform/loader/fetch/resource_load_scheduler.h

@@ -265,6 +265,8 @@ class PLATFORM_EXPORT ResourceLoadScheduler final
 
   size_t GetOutstandingLimit() const;
 
+  bool IsThrottledState() const;
+
   // A flag to indicate an internal running state.
   // TODO(toyoshim): We may want to use enum once we start to have more states.
   bool is_shutdown_ = false;