Revert of Do V8 GC ASAP if system memory is pressured

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 648ac5128c2e7591af92b4c70b3456027cd6088c..fdba7c596ae48e0f141bcbae111a34a971994741 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -161,6 +161,7 @@
 #include "third_party/skia/include/core/SkGraphics.h"
 #include "ui/base/layout.h"
 #include "ui/base/ui_base_switches.h"
+#include "v8/include/v8.h"
 
 #if defined(OS_ANDROID)
 #include <cpu-features.h>
@@ -240,17 +241,6 @@
 // incorrectly from the wrong thread.
 base::LazyInstance<base::ThreadLocalPointer<RenderThreadImpl> >
     lazy_tls = LAZY_INSTANCE_INITIALIZER;
-
-// v8::MemoryPressureLevel should correspond to base::MemoryPressureListener.
-static_assert(static_cast<v8::MemoryPressureLevel>(
-    base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE) ==
-        v8::MemoryPressureLevel::kNone, "none level not align");
-static_assert(static_cast<v8::MemoryPressureLevel>(
-    base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE) ==
-        v8::MemoryPressureLevel::kModerate, "moderate level not align");
-static_assert(static_cast<v8::MemoryPressureLevel>(
-    base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL) ==
-        v8::MemoryPressureLevel::kCritical, "critical level not align");
 
 class WebThreadForCompositor : public WebThreadImplForWorkerScheduler {
  public:
@@ -356,6 +346,13 @@
   if (!isolate)
     return;
   v8::Date::DateTimeConfigurationChangeNotification(isolate);
+}
+
+void LowMemoryNotificationOnThisThread() {
+  v8::Isolate* isolate = v8::Isolate::GetCurrent();
+  if (!isolate)
+    return;
+  isolate->LowMemoryNotification();
 }
 
 class RenderFrameSetupImpl : public mojom::RenderFrameSetup {
@@ -826,9 +823,7 @@
 #endif
 
   memory_pressure_listener_.reset(new base::MemoryPressureListener(
-      base::Bind(&RenderThreadImpl::OnMemoryPressure, base::Unretained(this)),
-      base::Bind(&RenderThreadImpl::OnSyncMemoryPressure,
-                 base::Unretained(this))));
+      base::Bind(&RenderThreadImpl::OnMemoryPressure, base::Unretained(this))));
 
   int num_raster_threads = 0;
   std::string string_value =
@@ -1936,13 +1931,25 @@
 
 void RenderThreadImpl::OnMemoryPressure(
     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
-  TRACE_EVENT0("memory","RenderThreadImpl::OnMemoryPressure");
   ReleaseFreeMemory();
 
   // Do not call into blink if it is not initialized.
   if (blink_platform_impl_) {
     blink::WebMemoryPressureListener::onMemoryPressure(
         static_cast<blink::WebMemoryPressureLevel>(memory_pressure_level));
+
+    if (blink::mainThreadIsolate()) {
+      // Trigger full v8 garbage collection on memory pressure notifications.
+      // This will potentially hang the renderer for a long time, however, when
+      // we receive a memory pressure notification, we might be about to be
+      // killed. Because of the janky hang don't do this to foreground
+      // renderers.
+      if (RendererIsHidden()) {
+        blink::mainThreadIsolate()->LowMemoryNotification();
+        RenderThread::Get()->PostTaskToAllWebWorkers(
+            base::Bind(&LowMemoryNotificationOnThisThread));
+      }
+    }
 
     if (memory_pressure_level ==
         base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL) {
@@ -2104,24 +2111,4 @@
   DCHECK_EQ(1u, erased);
 }
 
-void RenderThreadImpl::OnSyncMemoryPressure(
-    base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
-  if (!blink::mainThreadIsolate())
-    return;
-
-  v8::MemoryPressureLevel v8_memory_pressure_level =
-      static_cast<v8::MemoryPressureLevel>(memory_pressure_level);
-
-  // In order to reduce performance impact, translate critical level to
-  // moderate level for foregroud renderer.
-  if (!RendererIsHidden() &&
-      v8_memory_pressure_level == v8::MemoryPressureLevel::kCritical)
-    v8_memory_pressure_level = v8::MemoryPressureLevel::kModerate;
-
-  blink::mainThreadIsolate()->MemoryPressureNotification(
-      v8_memory_pressure_level);
-  blink::MemoryPressureNotificationToWorkerThreadIsolates(
-      v8_memory_pressure_level);
-}
-
 }  // namespace content