Fix num_threads to avoid divide by zero error when running without a thread pool

Signed-off-by: teymour-aldridge <teymour.aldridge@icloud.com>

2 files changed, 8 insertions, 4 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 7446e13a3b5..7cb926f10a4 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -1404,7 +1404,7 @@ impl LayoutThread {
         let pool;
         let (thread_pool, num_threads) = if self.parallel_flag {
             pool = STYLE_THREAD_POOL.pool();
-            (pool.as_ref(), STYLE_THREAD_POOL.num_threads)
+            (pool.as_ref(), STYLE_THREAD_POOL.num_threads.unwrap_or(1))
         } else {
             (None, 1)
         };
diff --git a/components/style/global_style_data.rs b/components/style/global_style_data.rs
index a9e79bf6820..872d97745f4 100644
--- a/components/style/global_style_data.rs
+++ b/components/style/global_style_data.rs
@@ -26,8 +26,8 @@ pub struct GlobalStyleData {
 
 /// Global thread pool.
 pub struct StyleThreadPool {
-    /// How many threads parallel styling can use.
-    pub num_threads: usize,
+    /// How many threads parallel styling can use. If not using a thread pool, this is set to `None`.
+    pub num_threads: Option<usize>,
 
     /// The parallel styling thread pool.
     ///
@@ -160,7 +160,11 @@ lazy_static! {
         };
 
         StyleThreadPool {
-            num_threads,
+            num_threads: if num_threads > 0 {
+                Some(num_threads)
+            } else {
+                None
+            },
             style_thread_pool: RwLock::new(pool),
         }
     };