Bug 1610738 - Add primitive flag to specify a compositor surface is p…

…referred r=sotaro

This allows calling code to specify whether a primitive would prefer
to be promoted to a compositor surface and/or picture cache slice.

This is a performance hint that can be used for large external
primitives, such as videos and canvas elements.

Differential Revision: https://phabricator.services.mozilla.com/D60637

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/71ed65a465d2bcfcf8e02ab8779c6700754ccdb2

webrender/src/picture.rs

@@ -2985,6 +2985,10 @@ bitflags! {
         const SCROLLBAR_CONTAINER = 64;
         /// If set, this cluster contains clear rectangle primitives.
         const IS_CLEAR_PRIMITIVE = 128;
+        /// This is used as a performance hint - this primitive may be promoted to a native
+        /// compositor surface under certain (implementation specific) conditions. This
+        /// is typically used for large videos, and canvas elements.
+        const PREFER_COMPOSITOR_SURFACE = 256;
     }
 }
 
@@ -3112,6 +3116,10 @@ impl PrimitiveList {
             flags.insert(ClusterFlags::SCROLLBAR_CONTAINER);
         }
 
+        if prim_flags.contains(PrimitiveFlags::PREFER_COMPOSITOR_SURFACE) {
+            flags.insert(ClusterFlags::PREFER_COMPOSITOR_SURFACE);
+        }
+
         // Insert the primitive into the first or last cluster as required
         match insert_position {
             PrimitiveListPosition::Begin => {

webrender_api/src/display_item.rs

@@ -43,6 +43,10 @@ bitflags! {
         const IS_SCROLLBAR_CONTAINER = 1 << 1;
         /// If set, this primitive represents a scroll bar thumb
         const IS_SCROLLBAR_THUMB = 1 << 2;
+        /// This is used as a performance hint - this primitive may be promoted to a native
+        /// compositor surface under certain (implementation specific) conditions. This
+        /// is typically used for large videos, and canvas elements.
+        const PREFER_COMPOSITOR_SURFACE = 1 << 3;
     }
 }
 

webrender_api/src/image.rs

@@ -251,10 +251,6 @@ bitflags! {
         ///
         /// See https://github.com/servo/webrender/pull/2555/
         const ALLOW_MIPMAPS = 2;
-        /// This is used as a performance hint - this image may be promoted to a native
-        /// compositor surface under certain (implementation specific) conditions. This
-        /// is typically used for large videos, and canvas elements.
-        const PREFER_COMPOSITOR_SURFACE = 4;
     }
 }
 
@@ -325,12 +321,6 @@ impl ImageDescriptor {
     pub fn allow_mipmaps(&self) -> bool {
         self.flags.contains(ImageDescriptorFlags::ALLOW_MIPMAPS)
     }
-
-    /// Returns true if this descriptor wants to be drawn as a native
-    /// compositor surface.
-    pub fn prefer_compositor_surface(&self) -> bool {
-        self.flags.contains(ImageDescriptorFlags::PREFER_COMPOSITOR_SURFACE)
-    }
 }
 
 /// Represents the backing store of an arbitrary series of pixels for display by