Bug 1376964 - Part 10: Allow style worker threads to pick fonts out of the user font cache. r=jfkthame

MozReview-Commit-ID: FX0T5ltA2u4

--HG--
extra : rebase_source : fc8a271f5ae1e0a897cd051b30da252be4176a4e

gfx/thebes/gfxUserFontSet.cpp

@@ -474,6 +474,12 @@ gfxUserFontEntry::ContinueLoad()
     }
 }
 
+static bool
+IgnorePrincipal(gfxFontSrcURI* aURI)
+{
+    return aURI->InheritsSecurityContext();
+}
+
 void
 gfxUserFontEntry::DoLoadNextSrc(bool aForceAsync)
 {
@@ -535,9 +541,16 @@ gfxUserFontEntry::DoLoadNextSrc(bool aForceAsync)
                     currSrc.mFormatFlags)) {
 
                 if (ServoStyleSet* set = ServoStyleSet::Current()) {
-                    set->AppendTask(PostTraversalTask::LoadFontEntry(this));
-                    SetLoadState(STATUS_LOAD_PENDING);
-                    return;
+                    // Only support style worker threads synchronously getting
+                    // entries from the font cache when it's not a data: URI
+                    // @font-face that came from UA or user sheets, since we
+                    // were not able to call IsFontLoadAllowed ahead of time
+                    // for these entries.
+                    if (currSrc.mUseOriginPrincipal && IgnorePrincipal(currSrc.mURI)) {
+                        set->AppendTask(PostTraversalTask::LoadFontEntry(this));
+                        SetLoadState(STATUS_LOAD_PENDING);
+                        return;
+                    }
                 }
 
                 gfxFontSrcPrincipal* principal = nullptr;
@@ -567,6 +580,14 @@ gfxUserFontEntry::DoLoadNextSrc(bool aForceAsync)
                         }
                     }
 
+                    if (ServoStyleSet* set = ServoStyleSet::Current()) {
+                        // If we need to start a font load and we're on a style
+                        // worker thread, we have to defer it.
+                        set->AppendTask(PostTraversalTask::LoadFontEntry(this));
+                        SetLoadState(STATUS_LOAD_PENDING);
+                        return;
+                    }
+
                     // record the principal returned by CheckFontLoad,
                     // for use when creating a channel
                     // and when caching the loaded entry
@@ -1136,12 +1157,6 @@ gfxUserFontSet::UserFontCache::Flusher::Observe(nsISupports* aSubject,
     return NS_OK;
 }
 
-static bool
-IgnorePrincipal(gfxFontSrcURI* aURI)
-{
-    return aURI->InheritsSecurityContext();
-}
-
 bool
 gfxUserFontSet::UserFontCache::Entry::KeyEquals(const KeyTypePointer aKey) const
 {