Bug 1355147 - Expose IsHeadless on GfxInfo. r=jrmuizel

Allows marionette to check if the browser is in headless mode.

MozReview-Commit-ID: 2kaqO3HO9Ke

widget/GfxInfoBase.cpp

@@ -1472,6 +1472,13 @@ GfxInfoBase::GetWebRenderEnabled(bool* aWebRenderEnabled)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+GfxInfoBase::GetIsHeadless(bool* aIsHeadless)
+{
+  *aIsHeadless = gfxPlatform::IsHeadless();
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 GfxInfoBase::GetContentBackend(nsAString & aContentBackend)
 {

widget/GfxInfoBase.h

@@ -62,6 +62,7 @@ public:
   NS_IMETHOD GetContentBackend(nsAString & aContentBackend) override;
   NS_IMETHOD GetUsingGPUProcess(bool *aOutValue) override;
   NS_IMETHOD GetWebRenderEnabled(bool* aWebRenderEnabled) override;
+  NS_IMETHOD GetIsHeadless(bool* aIsHeadless) override;
 
   // Initialization function. If you override this, you must call this class's
   // version of Init first.

widget/nsIGfxInfo.idl

@@ -24,6 +24,7 @@ interface nsIGfxInfo : nsISupports
    */
   readonly attribute DOMString ContentBackend;
   readonly attribute boolean WebRenderEnabled;
+  readonly attribute boolean isHeadless;
 
   // XXX: Switch to a list of devices, rather than explicitly numbering them.