Bug 1411532 part 1 - Add a pref for enabling stylo on chrome document…

…s. r=bz MozReview-Commit-ID: 7Zbh4Mf43xC --HG-- extra : rebase_source : f9e4d0b6d1234cb8efcfbaaab2a349d2a082dd6e
dothq · Oct 27, 2017 · b24625e · b24625e
1 parent 59e80b6
commit b24625e
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Showing 4 changed files with 47 additions and 5 deletions.
diff --git a/dom/ipc/ContentPrefs.cpp b/dom/ipc/ContentPrefs.cpp
@@ -122,6 +122,7 @@ const char* mozilla::dom::ContentPrefs::gInitPrefs[] = {
   "javascript.use_us_english_locale",
   "jsloader.shareGlobal",
 #ifdef MOZ_STYLO
+  "layout.css.servo.chrome.enabled",
   "layout.css.stylo-blocklist.blocked_domains",
   "layout.css.stylo-blocklist.enabled",
 #endif

diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
@@ -8152,7 +8152,8 @@ nsLayoutUtils::ShouldUseStylo(nsIURI* aDocumentURI, nsIPrincipal* aPrincipal)
   // supported. Other principal aren't able to use XUL by default, and
   // the back door to enable XUL is mostly just for testing, which means
   // they don't matter, and we shouldn't respect them at the same time.
-  if (nsContentUtils::IsSystemPrincipal(aPrincipal)) {
+  if (!StyloChromeEnabled() &&
+      nsContentUtils::IsSystemPrincipal(aPrincipal)) {
     return false;
   }
   // Check any internal page which we need to explicitly blacklist.
@@ -8232,6 +8233,21 @@ nsLayoutUtils::RemoveFromStyloBlocklist(const nsACString& aBlockedDomain)
     sStyloBlocklist = nullptr;
   }
 }
+
+/* static */
+bool
+nsLayoutUtils::StyloChromeEnabled()
+{
+  static bool sInitialized = false;
+  static bool sEnabled = false;
+  if (!sInitialized) {
+    // We intentionally don't allow dynamic toggling of this pref
+    // because it is rather risky to mix style backend in XUL.
+    sEnabled = Preferences::GetBool("layout.css.servo.chrome.enabled");
+    sInitialized = true;
+  }
+  return sEnabled;
+}
 #endif
 
 /* static */

diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h
@@ -2526,13 +2526,33 @@ class nsLayoutUtils
 #endif
   }
 
-  // Whether Stylo should be allowed to be enabled in this process.  This
-  // returns true for content processes and the non-e10s parent process.
+  // Whether Stylo should be allowed to be enabled in this process.
   static bool StyloSupportedInCurrentProcess() {
-     return XRE_IsContentProcess() ||
-            (XRE_IsParentProcess() && !XRE_IsE10sParentProcess());
+#ifdef MOZ_STYLO
+    if (XRE_IsContentProcess()) {
+      return true;
+    }
+    if (XRE_IsParentProcess()) {
+      // If Stylo is enabled for chrome document, we use it in all
+      // parent processes, regardless of whether it's e10s parent.
+      if (StyloChromeEnabled()) {
+        return true;
+      }
+      // Otherwise we only use stylo on non-e10s parent.
+      return !XRE_IsE10sParentProcess();
+    }
+#endif
+    // Stylo is not enabled for any other process.
+    MOZ_DIAGNOSTIC_ASSERT(false, "We should not be creating any document "
+                          "in processes other than content and parent");
+    return false;
   }
 
+#ifdef MOZ_STYLO
+  // Whether Stylo should be used on chrome documents.
+  static bool StyloChromeEnabled();
+#endif
+
   static uint32_t IdlePeriodDeadlineLimit() {
     return sIdlePeriodDeadlineLimit;
   }

diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
@@ -5818,6 +5818,11 @@ pref("layout.css.servo.enabled", true);
 #else
 pref("layout.css.servo.enabled", false);
 #endif
+// Whether Stylo is enabled for chrome document?
+// If Stylo is not enabled, this pref doesn't take any effect.
+// Note that this pref is only read once when requested. Changing it
+// at runtime may have no effect.
+pref("layout.css.servo.chrome.enabled", false);
 #endif
 
 // HSTS Priming