ProcessingInstruction should not remove pending sheets when is_xsl_.

Because ProcessingInstruction::Process only invokes AddPendingSheet when !is_xsl_. If removing pending sheets, StyleEngine will not find whether all pending parser blocking stylesheets are loaded or not correctly.

Bug: 905827, 1035293
Change-Id: Id617c2001601bef6e4e867ea1a193d5b4e8a51fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1978540Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/master@{#726724}

third_party/blink/renderer/core/dom/processing_instruction.cc

@@ -283,6 +283,8 @@ void ProcessingInstruction::ClearSheet() {
 }
 
 void ProcessingInstruction::RemovePendingSheet() {
+  if (is_xsl_)
+    return;
   GetDocument().GetStyleEngine().RemovePendingSheet(*this,
                                                     style_engine_context_);
 }

third_party/blink/web_tests/TestExpectations

@@ -5149,9 +5149,6 @@ crbug.com/902645 [ Retina ] transforms/3d/point-mapping/3d-point-mapping-origins
 # Test is flaky under load
 crbug.com/904389 http/tests/preload/delaying_onload_link_preload_after_discovery.html [ Failure Pass ]
 
-#Sheriff 2018-11-14
-crbug.com/905827 fast/dom/StyleSheet/stylesheet-move-between-documents-crash.html [ Skip ]
-
 # Flaky crash due to "bad mojo message".
 crbug.com/906952 editing/pasteboard/file-drag-to-editable.html [ Pass Crash ]
 
@@ -6087,7 +6084,6 @@ crbug.com/1034789 [ Mac10.13 ] http/tests/security/frameNavigation/xss-ALLOWED-p
 crbug.com/1034789 [ Mac10.13 ] virtual/threaded/fast/scroll-snap/snap-to-target-on-layout-change.html [ Pass Timeout ]
 crbug.com/1034789 [ Mac10.13 ] external/wpt/pointerevents/pointerevent_coalesced_events_attributes.html [ Pass Failure ]
 crbug.com/1034839 css3/filters/effect-reference-image.html [ Pass Failure ]
-crbug.com/1035293 virtual/web-components-v0-disabled/fast/dom/StyleSheet/stylesheet-move-between-documents-crash.html [ Pass Crash ]
 
 # Sheriff 2019-12-18
 crbug.com/859169 http/tests/devtools/layers/layer-compositing-reasons.js [ Pass Failure ]