NOT FOR COMMIT: Move background pausing to the WebView level

third_party/WebKit/Source/platform/scheduler/renderer/web_view_scheduler_impl.cc

Index: third_party/WebKit/Source/platform/scheduler/renderer/web_view_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/web_view_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/web_view_scheduler_impl.cc
index 500c89a5ab96c5d9bc8bfdef2f391d834e7d20f3..6898a52d8409e9ba950c0fc5117c28f5f48ad00e 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/web_view_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/web_view_scheduler_impl.cc
@@ -5,7 +5,10 @@
 #include "platform/scheduler/renderer/web_view_scheduler_impl.h"
 
 #include "base/logging.h"
+#include "base/memory/memory_coordinator_client_registry.h"
 #include "base/strings/stringprintf.h"
+// TODO(ojan): This is disallowed by build rules?
+#include "chrome/common/pause_tabs_field_trial.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/WebFrameScheduler.h"
 #include "platform/scheduler/base/virtual_time_domain.h"
@@ -14,6 +17,7 @@
 #include "platform/scheduler/renderer/budget_pool.h"
 #include "platform/scheduler/renderer/renderer_scheduler_impl.h"
 #include "platform/scheduler/renderer/web_frame_scheduler_impl.h"
+// #include "public/platform/Platform.h"
 
 namespace blink {
 namespace scheduler {
@@ -31,8 +35,13 @@ constexpr base::TimeDelta kDefaultMaxBackgroundThrottlingDelay =
     base::TimeDelta::FromMinutes(1);
 constexpr base::TimeDelta kDefaultInitialBackgroundBudget =
     base::TimeDelta::FromSeconds(1);
+// TODO(ojan): Make this 10 seconds. This is just for easy testing.
 constexpr base::TimeDelta kBackgroundThrottlingGracePeriod =
-    base::TimeDelta::FromSeconds(10);
+    base::TimeDelta::FromSeconds(100);
+// TODO(ojan): Make this 5 minutes. This is just for testing.
+constexpr base::TimeDelta kBackgroundPausingDelay =
+    base::TimeDelta::FromSeconds(3);
+
 
 // Values coming from WebViewSchedulerSettings are interpreted as follows:
 //   -1 is "not set". Scheduler should use a reasonable default.
@@ -118,6 +127,10 @@ WebViewSchedulerImpl::WebViewSchedulerImpl(
   delayed_background_throttling_enabler_.Reset(
       base::Bind(&WebViewSchedulerImpl::EnableBackgroundThrottling,
                  base::Unretained(this)));
+
+  background_pauser_.Reset(
+      base::Bind(&WebViewSchedulerImpl::EnableBackgroundSuspension,
+                 base::Unretained(this)));
 }
 
 WebViewSchedulerImpl::~WebViewSchedulerImpl() {
@@ -395,13 +408,37 @@ void WebViewSchedulerImpl::EnableBackgroundThrottling() {
   UpdateBackgroundBudgetPoolThrottlingState();
 }
 
+void WebViewSchedulerImpl::EnableBackgroundSuspension() {
+  for (WebFrameSchedulerImpl* frame_scheduler : frame_schedulers_) {
+    frame_scheduler->SetSuspended(true);
+  }
+  UpdateBackgroundBudgetPoolThrottlingState();
+
+  // TODO(tasak|bashi): We should use ChildMemoryCoordinator here, but
+  // ChildMemoryCoordinator isn't always available as it's only initialized
+  // when kMemoryCoordinatorV0 is enabled.
+  // Use ChildMemoryCoordinator when memory coordinator is always enabled.
+  base::MemoryCoordinatorClientRegistry::GetInstance()->PurgeMemory();
+}
+
+bool WebViewSchedulerImpl::ShouldSuspendWhenBackgrounded() {
+#if defined(OS_ANDROID)
+  return true;
+#else
+  // TODO(ojan): Hook this up to site engagement.
+  return base::FeatureList::IsEnabled(pausetabs::kFeature);
+#endif
+}
+
 void WebViewSchedulerImpl::UpdateBackgroundThrottlingState() {
   delayed_background_throttling_enabler_.Cancel();
+  background_pauser_.Cancel();
 
   if (page_visible_) {
     should_throttle_frames_ = false;
     for (WebFrameSchedulerImpl* frame_scheduler : frame_schedulers_) {
       frame_scheduler->SetPageThrottled(false);
+      frame_scheduler->SetSuspended(false);
     }
     UpdateBackgroundBudgetPoolThrottlingState();
   } else {
@@ -413,6 +450,12 @@ void WebViewSchedulerImpl::UpdateBackgroundThrottlingState() {
       renderer_scheduler_->ControlTaskQueue()->PostDelayedTask(
           FROM_HERE, delayed_background_throttling_enabler_.GetCallback(),
           kBackgroundThrottlingGracePeriod);
+
+      if (ShouldSuspendWhenBackgrounded()) {
+        renderer_scheduler_->ControlTaskQueue()->PostDelayedTask(
+            FROM_HERE, background_pauser_.GetCallback(),
+            kBackgroundPausingDelay);
+      }
     }
   }
 }