Remove pageVisibility option

The original purpose of this option is not working anymore, also adds
docs on the current way to disable process backgrounding.

atom/browser/web_contents_preferences.cc

@@ -34,8 +34,6 @@ FeaturePair kWebRuntimeFeatures[] = {
     switches::kExperimentalFeatures },
   { options::kExperimentalCanvasFeatures,
     switches::kExperimentalCanvasFeatures },
-  { options::kPageVisibility,
-    switches::kPageVisibility },
 };
 
 }  // namespace

atom/common/options_switches.cc

@@ -85,9 +85,6 @@ const char kNodeIntegration[] = "nodeIntegration";
 // Instancd ID of guest WebContents.
 const char kGuestInstanceID[] = "guestInstanceId";
 
-// Set page visiblity to always visible.
-const char kPageVisibility[] = "pageVisibility";
-
 // Enable DirectWrite on Windows.
 const char kDirectWrite[] = "directWrite";
 
@@ -141,7 +138,6 @@ const char kNodeIntegration[]            = "node-integration";
 const char kGuestInstanceID[]            = "guest-instance-id";
 const char kExperimentalFeatures[]       = "experimental-features";
 const char kExperimentalCanvasFeatures[] = "experimental-canvas-features";
-const char kPageVisibility[]             = "page-visiblity";
 const char kOpenerID[]                   = "opener-id";
 
 // Widevine options

atom/common/options_switches.h

@@ -49,7 +49,6 @@ extern const char kNodeIntegration[];
 extern const char kGuestInstanceID[];
 extern const char kExperimentalFeatures[];
 extern const char kExperimentalCanvasFeatures[];
-extern const char kPageVisibility[];
 extern const char kOpenerID[];
 
 }   // namespace options
@@ -77,7 +76,6 @@ extern const char kNodeIntegration[];
 extern const char kGuestInstanceID[];
 extern const char kExperimentalFeatures[];
 extern const char kExperimentalCanvasFeatures[];
-extern const char kPageVisibility[];
 extern const char kOpenerID[];
 
 extern const char kWidevineCdmPath[];

atom/renderer/atom_renderer_client.cc

@@ -210,19 +210,6 @@ content::BrowserPluginDelegate* AtomRendererClient::CreateBrowserPluginDelegate(
   }
 }
 
-bool AtomRendererClient::ShouldOverridePageVisibilityState(
-    const content::RenderFrame* render_frame,
-    blink::WebPageVisibilityState* override_state) {
-  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
-
-  if (IsSwitchEnabled(command_line, switches::kPageVisibility)) {
-    *override_state = blink::WebPageVisibilityStateVisible;
-    return true;
-  }
-
-  return false;
-}
-
 void AtomRendererClient::EnableWebRuntimeFeatures() {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
 

atom/renderer/atom_renderer_client.h

@@ -56,9 +56,6 @@ class AtomRendererClient : public content::ContentRendererClient,
       content::RenderFrame* render_frame,
       const std::string& mime_type,
       const GURL& original_url) override;
-  bool ShouldOverridePageVisibilityState(
-      const content::RenderFrame* render_frame,
-      blink::WebPageVisibilityState* override_state) override;
   void AddKeySystems(std::vector<media::KeySystemInfo>* key_systems) override;
 
   void EnableWebRuntimeFeatures();