REGRESSION (Sonoma): [ Sonoma wk2 Release ] compositing/reflections/r…

…epaint-with-reflection.html is flaky

https://bugs.webkit.org/show_bug.cgi?id=263347
rdar://117172843

Reviewed by Tim Horton.

Increase the scope of having a non-null `m_currentTransaction` in `RemoteLayerTreeContext::buildTransaction()`,
since `paintReachableBackingStoreContents()` can call `PlatformCALayerRemote::copyContentsFromLayer()` for
layers with reflections, and we need `RemoteLayerTreeContext::layerPropertyChangedWhileBuildingTransaction()`
to see `m_currentTransaction` so we mark the clone as having changed properties.

* LayoutTests/platform/mac-wk2/TestExpectations:
* Source/WebKit/WebProcess/WebPage/RemoteLayerTree/RemoteLayerTreeContext.mm:
(WebKit::RemoteLayerTreeContext::buildTransaction):

Canonical link: https://commits.webkit.org/270082@main

LayoutTests/platform/mac-wk2/TestExpectations

@@ -2010,8 +2010,6 @@ webkit.org/b/263282 [ Sonoma+ ] fast/replaced/replaced-breaking.html [ Failure ]
 
 webkit.org/b/263296 [ Sonoma+ arm64 ] compositing/hidpi-compositing-layer-with-tile-layers-on-subpixel-position.html [ ImageOnlyFailure ]
 
-webkit.org/b/263347 [ Sonoma+ Release ] compositing/reflections/repaint-with-reflection.html [ Pass ImageOnlyFailure ]
-
 webkit.org/b/261356 [ Debug ] fast/mediastream/device-change-event-2.html [ Pass Timeout ] # CHANGE TO [ Pass Timeout ] WITHOUT DEBUG AFTER FIX ACCORDING TO webkit.org/b/188924
 
 webkit.org/b/263396 css3/color/text.html [ Skip ]

Source/WebKit/WebProcess/WebPage/RemoteLayerTree/RemoteLayerTreeContext.mm

@@ -197,12 +197,13 @@
     m_currentTransaction = &transaction;
     rootLayerRemote.recursiveBuildTransaction(*this, transaction);
     m_backingStoreCollection->prepareBackingStoresForDisplay(transaction);
-    m_currentTransaction = nullptr;
 
     bool paintedAnyBackingStore = m_backingStoreCollection->paintReachableBackingStoreContents();
     if (paintedAnyBackingStore)
         m_nextRenderingUpdateRequiresSynchronousImageDecoding = false;
 
+    m_currentTransaction = nullptr;
+
     transaction.setCreatedLayers(moveToVector(std::exchange(m_createdLayers, { }).values()));
     transaction.setDestroyedLayerIDs(WTFMove(m_destroyedLayers));
 }