With this change, Intelligent Session Restore checks the memory pressure

level before restoring each tab and aborts tab restore if pressure exists.
This is especially important on the Mac where the delay between memory
pressure events and receiving notifications of those events can be so long
that tab restore completes before the notification arrives.

BUG=547215

Review URL: https://codereview.chromium.org/1421903002

Cr-Commit-Position: refs/heads/master@{#356157}

1 files changed, 18 insertions, 13 deletions

diff --git a/chrome/browser/sessions/tab_loader.cc b/chrome/browser/sessions/tab_loader.cc
index 05ec0bf..f645c86 100644
--- a/chrome/browser/sessions/tab_loader.cc
+++ b/chrome/browser/sessions/tab_loader.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 #include <string>
 
+#include "base/memory/memory_pressure_monitor.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/sessions/session_restore_stats_collector.h"
@@ -22,12 +23,6 @@
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
 
-#if defined(OS_WIN)
-#include "base/memory/memory_pressure_monitor_win.h"
-#elif defined(OS_MACOSX) && !defined(OS_IOS)
-#include "base/memory/memory_pressure_monitor_mac.h"
-#endif
-
 using content::NavigationController;
 using content::RenderWidgetHost;
 using content::WebContents;
@@ -152,6 +147,19 @@ void TabLoader::LoadNextTab() {
   // loading.
   CHECK(delegate_);
   if (!tabs_to_load_.empty()) {
+    // Check the memory pressure before restoring the next tab, and abort if
+    // there is pressure. This is important on the Mac because of the sometimes
+    // large delay between a memory pressure event and receiving a notification
+    // of that event (in that case tab restore can trigger memory pressure but
+    // will complete before the notification arrives).
+    base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level =
+        CurrentMemoryPressureLevel();
+    if (memory_pressure_level !=
+        base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE) {
+      OnMemoryPressure(memory_pressure_level);
+      return;
+    }
+
     NavigationController* controller = tabs_to_load_.front();
     DCHECK(controller);
     tabs_loading_.insert(controller);
@@ -233,14 +241,11 @@ base::MemoryPressureListener::MemoryPressureLevel
   // Check for explicit memory pressure integration.
   std::string react_to_memory_pressure = variations::GetVariationParamValue(
       "IntelligentSessionRestore", "ReactToMemoryPressure");
-  if (react_to_memory_pressure == "true") {
-#if defined(OS_WIN)
-    return base::win::MemoryPressureMonitor::Get()->GetCurrentPressureLevel();
-#else
-    return base::mac::MemoryPressureMonitor::Get()->GetCurrentPressureLevel();
-#endif
-  }
+  if (react_to_memory_pressure != "true")
+    return base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
 #endif  // defined(OS_WIN) || (defined(OS_MACOSX) && !defined(OS_IOS))
+  if (base::MemoryPressureMonitor::Get())
+    return base::MemoryPressureMonitor::Get()->GetCurrentPressureLevel();
 
   return base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
 }