Bug 1366356 - Decrease the process priority of content processes that are not running a foreground tab - part 2 - enabled if the platform specific code is ready, r=smaug

dom/ipc/ProcessPriorityManager.cpp

@@ -332,7 +332,7 @@ ProcessPriorityManagerImpl::PrefChangedCallback(const char* aPref,
 /* static */ bool
 ProcessPriorityManagerImpl::PrefsEnabled()
 {
-  return sPrefsEnabled && !sRemoteTabsDisabled;
+  return sPrefsEnabled && hal::SetProcessPrioritySupported() && !sRemoteTabsDisabled;
 }
 
 /* static */ bool

hal/Hal.cpp

@@ -850,6 +850,12 @@ NotifySwitchChange(const SwitchEvent& aEvent)
   observer.Broadcast(aEvent);
 }
 
+bool
+SetProcessPrioritySupported()
+{
+  RETURN_PROXY_IF_SANDBOXED(SetProcessPrioritySupported(), false);
+}
+
 void
 SetProcessPriority(int aPid, ProcessPriority aPriority)
 {

hal/Hal.h

@@ -430,6 +430,12 @@ hal::SwitchState GetCurrentSwitchState(hal::SwitchDevice aDevice);
 void NotifySwitchStateFromInputDevice(hal::SwitchDevice aDevice,
                                       hal::SwitchState aState);
 
+/**
+ * Return true if the current platform supports the setting of process
+ * priority.
+ */
+bool SetProcessPrioritySupported();
+
 /**
  * Set the priority of the given process.
  *

hal/fallback/FallbackProcessPriority.cpp

@@ -10,6 +10,12 @@ using namespace mozilla::hal;
 namespace mozilla {
 namespace hal_impl {
 
+bool
+SetProcessPrioritySupported()
+{
+  return false;
+}
+
 void
 SetProcessPriority(int aPid, ProcessPriority aPriority)
 {

hal/sandbox/SandboxHal.cpp

@@ -354,6 +354,13 @@ SetProcessPriority(int aPid, ProcessPriority aPriority)
   NS_RUNTIMEABORT("Only the main process may set processes' priorities.");
 }
 
+bool
+SetProcessPrioritySupported()
+{
+  NS_RUNTIMEABORT("Only the main process may call SetProcessPrioritySupported().");
+  return false;
+}
+
 void
 SetCurrentThreadPriority(ThreadPriority aThreadPriority)
 {