[CoordinatedGraphics] CoordinatedPlatformLayer should accumulate damage

https://bugs.webkit.org/show_bug.cgi?id=290164

Reviewed by Alejandro G. Castro.

We currently replace current damage with the given one, but in case of
multiple layer flushes before the composition, the damage should be
accumulated.

* Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedPlatformLayer.cpp:
(WebCore::CoordinatedPlatformLayer::setDamage):
(WebCore::CoordinatedPlatformLayer::flushCompositingState):
* Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedPlatformLayer.h:

Canonical link: https://commits.webkit.org/292582@main

Author: carlosgcampos

Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedPlatformLayer.cpp

@@ -562,7 +562,11 @@ void CoordinatedPlatformLayer::setDirtyRegion(Vector<IntRect, 1>&& dirtyRegion)
 void CoordinatedPlatformLayer::setDamage(Damage&& damage)
 {
     ASSERT(m_lock.isHeld());
-    m_damage = WTFMove(damage);
+
+    if (!m_damage)
+        m_damage = WTFMove(damage);
+    else
+        m_damage->add(damage);
     m_pendingChanges.add(Change::Damage);
 }
 #endif
@@ -908,8 +912,11 @@ void CoordinatedPlatformLayer::flushCompositingState(TextureMapper& textureMappe
         layer.setSolidColor(m_contentsColor);
 
 #if ENABLE(DAMAGE_TRACKING)
-    if (m_pendingChanges.contains(Change::Damage))
-        layer.setDamage(WTFMove(m_damage));
+    if (m_pendingChanges.contains(Change::Damage)) {
+        ASSERT(m_damage.has_value());
+        layer.setDamage(WTFMove(*m_damage));
+        m_damage = std::nullopt;
+    }
 #endif
 
     if (m_pendingChanges.contains(Change::Filters))

Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedPlatformLayer.h

@@ -296,7 +296,7 @@ class CoordinatedPlatformLayer : public ThreadSafeRefCounted<CoordinatedPlatform
     float m_debugBorderWidth WTF_GUARDED_BY_LOCK(m_lock) { 0 };
     int m_repaintCount WTF_GUARDED_BY_LOCK(m_lock) { -1 };
 #if ENABLE(DAMAGE_TRACKING)
-    Damage m_damage WTF_GUARDED_BY_LOCK(m_lock);
+    std::optional<Damage> m_damage WTF_GUARDED_BY_LOCK(m_lock);
 #endif
 #if ENABLE(SCROLLING_THREAD)
     Markable<ScrollingNodeID> m_scrollingNodeID WTF_GUARDED_BY_LOCK(m_lock);