Mac: Use Mavericks occlusion APIs for power savings.

content/browser/web_contents/web_contents_view_mac.mm

Index: content/browser/web_contents/web_contents_view_mac.mm
diff --git a/content/browser/web_contents/web_contents_view_mac.mm b/content/browser/web_contents/web_contents_view_mac.mm
index 42348a97bca9cd9c2c15006740f5fcafc521d603..b2e3dd71a0f4da1173d3f42949c469493d0235bf 100644
--- a/content/browser/web_contents/web_contents_view_mac.mm
+++ b/content/browser/web_contents/web_contents_view_mac.mm
@@ -8,6 +8,7 @@
 
 #include <string>
 
+#include "base/mac/mac_util.h"
 #import "base/mac/scoped_sending_event.h"
 #include "base/message_loop/message_loop.h"
 #import "base/message_loop/message_pump_mac.h"
@@ -594,4 +595,40 @@ void WebContentsViewMac::CloseTab() {
     [subview setFrame:self.bounds];
 }
 
+- (void)viewWillMoveToWindow:(NSWindow*)newWindow {
+  // Occlusion notification is new in Mavericks.
+  if (base::mac::IsOSMavericksOrLater())
+    return;
+
+  NSWindow* oldWindow = [self window];
+
+  if (oldWindow) {
+    [[NSNotificationCenter defaultCenter]
+        removeObserver:self
+                  name:NSWindowDidChangeOcclusionStateNotification
+                object:oldWindow];
+  }
+
+  if (newWindow) {
+    [[NSNotificationCenter defaultCenter]
+        addObserver:self
+           selector:@selector(windowChangedOcclusionState:)
+               name:NSWindowDidChangeOcclusionStateNotification
+             object:newWindow];
+  }
+}
+
+- (void)windowChangedOcclusionState:(NSNotification*)notification {
+  DCHECK(base::mac::IsOSMavericksOrLater());
+  NSWindow* window = [notification object];
+  WebContentsImpl* webContents = [self webContents];
+  if ([window occlusionState] & NSWindowOcclusionStateVisible) {
+    if (!webContents->should_normally_be_visible())
+      webContents->WasShown();
+  } else {
+    if (webContents->should_normally_be_visible())
+      webContents->WasHidden();
+  }
+}
+
 @end