CSS: shadow part map application was off-by-one.

The previous implementation gave the document the ability to forward a
part from sub-component of a component but only the component author
should be able to do that.

Bug: 859446, 805271
Change-Id: I37dc9399646a2db677c350546cbb1cfad7ee2d39
Reviewed-on: https://chromium-review.googlesource.com/1122136Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Reviewed-by: Anders Ruud <andruud@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572148}

third_party/WebKit/LayoutTests/css-shadow-parts/double-forward.html

@@ -17,11 +17,11 @@
       <span id="green_part" part="partp">This text</span>
     </template>
     <script>installCustomElement("custom-element-middle", "custom-element-middle-template");</script>
-    <template id="custom-element-middle-template"><custom-element-inner id="c-e-inner"></custom-element-inner></template>
+    <template id="custom-element-middle-template"><custom-element-inner id="c-e-inner" partmap="partp part-forwarded1"></custom-element-inner></template>
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
-    <template id="custom-element-outer-template"><custom-element-middle id="c-e-middle" partmap="partp part-forwarded1"></custom-element-middle></template>
+    <template id="custom-element-outer-template"><custom-element-middle id="c-e-middle" partmap="part-forwarded1 part-forwarded2"></custom-element-middle></template>
     The following text should be green:
-    <custom-element-outer id="c-e-outer" partmap="part-forwarded1 part-forwarded2"></custom-element-outer>
+    <custom-element-outer id="c-e-outer"></custom-element-outer>
     <script type="text/javascript">
       "use strict";
       const colorGreen = "rgb(0, 128, 0)";

third_party/WebKit/LayoutTests/css-shadow-parts/invalidation-change-part-name-forward.html

@@ -17,9 +17,9 @@
       <span id="part" part="partp">This text</span>
     </template>
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
-    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner"></custom-element-inner></template>
+    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner" partmap="partp part-forwarded"></custom-element-inner></template>
     The following text should be green:
-    <custom-element-outer id="c-e-outer" partmap="partp part-forwarded"></custom-element-outer>
+    <custom-element-outer id="c-e-outer"></custom-element-outer>
     <script type="text/javascript">
       "use strict";
       test(function() {

third_party/WebKit/LayoutTests/css-shadow-parts/invalidation-change-partmap-forward.html

@@ -17,15 +17,15 @@
       <span id="part" part="partp">This text</span>
     </template>
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
-    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner"></custom-element-inner></template>
+    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner" partmap="partp part-forwarded"></custom-element-inner></template>
     The following text should be green:
-    <custom-element-outer id="c-e-outer" partmap="partp part-forwarded"></custom-element-outer>
+    <custom-element-outer id="c-e-outer"></custom-element-outer>
     <script type="text/javascript">
       "use strict";
       test(function() {
         var part = getElementByShadowIds(document, ["c-e-outer", "c-e-inner", "part"]);
         var before = window.getComputedStyle(part).color;
-        document.getElementById("c-e-outer").setAttribute("partmap", "new-partmap");
+        getElementByShadowIds(document, ["c-e-outer", "c-e-inner"]).setAttribute("partmap", "new-partmap");
         var after = window.getComputedStyle(part).color;
         assert_not_equals(before, after);
       }, "Part in selected host changed color");

third_party/WebKit/LayoutTests/css-shadow-parts/invalidation-complex-selector-forward.html

@@ -17,9 +17,9 @@
       <span id="part" part="partp">This text</span>
     </template>
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
-    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner"></custom-element-inner></template>
+    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner" partmap="partp part-forwarded"></custom-element-inner></template>
     The following text should be green:
-    <div id="elem"><custom-element-outer id="c-e-outer" partmap="partp part-forwarded"></custom-element-outer></div>
+    <div id="elem"><custom-element-outer id="c-e-outer"></custom-element-outer></div>
     <script type="text/javascript">
       "use strict";
       test(function() {

third_party/WebKit/LayoutTests/css-shadow-parts/precedence-part-vs-part.html

@@ -19,10 +19,10 @@
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
     <template id="custom-element-outer-template">
       <style>#c-e-inner::part(partp) { color: red; }</style>
-      <custom-element-inner id="c-e-inner"></custom-element-inner>
+      <custom-element-inner id="c-e-inner" partmap="partp part-forwarded"></custom-element-inner>
     </template>
     The following text should be green:
-    <custom-element-outer id="c-e-outer" partmap="partp part-forwarded"></custom-element-outer>
+    <custom-element-outer id="c-e-outer"></custom-element-outer>
     <script type="text/javascript">
       "use strict";
       const colorGreen = "rgb(0, 128, 0)";

third_party/WebKit/LayoutTests/css-shadow-parts/simple-forward-shorthand.html

@@ -17,9 +17,9 @@
       <span id="green_part" part="partp">This text</span>
     </template>
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
-    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner"></custom-element-inner></template>
+    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner" partmap="partp"></custom-element-inner></template>
     The following text should be green:
-    <custom-element-outer id="c-e-outer" partmap="partp"></custom-element-outer>
+    <custom-element-outer id="c-e-outer"></custom-element-outer>
     <script type="text/javascript">
       "use strict";
       const colorGreen = "rgb(0, 128, 0)";

third_party/WebKit/LayoutTests/css-shadow-parts/simple-forward.html

@@ -17,9 +17,9 @@
       <span id="green_part" part="partp">This text</span>
     </template>
     <script>installCustomElement("custom-element-outer", "custom-element-outer-template");</script>
-    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner"></custom-element-inner></template>
+    <template id="custom-element-outer-template"><custom-element-inner id="c-e-inner" partmap="partp part-forwarded"></custom-element-inner></template>
     The following text should be green:
-    <custom-element-outer id="c-e-outer" partmap="partp part-forwarded"></custom-element-outer>
+    <custom-element-outer id="c-e-outer"></custom-element-outer>
     <script type="text/javascript">
       "use strict";
       const colorGreen = "rgb(0, 128, 0)";

third_party/blink/renderer/core/css/resolver/style_resolver.cc

@@ -280,17 +280,16 @@ void StyleResolver::MatchPseudoPartRules(const Element& element,
       collector.FinishAddingAuthorRulesForTreeScope();
     }
 
-    // We have reached the top-level document.
-    if (!(host = host->OwnerShadowHost()))
-      return;
-
-    // After the direct host of the element, if the host doesn't forward any
-    // parts using partmap= then the element is unreachable from any scope above
-    // and we can stop.
+    // If the host doesn't forward any parts using partmap= then the element is
+    // unreachable from any scope further above and we can stop.
     const NamesMap* part_map = host->PartNamesMap();
     if (!part_map)
       return;
 
+    // We have reached the top-level document.
+    if (!(host = host->OwnerShadowHost()))
+      return;
+
     current_names.PushMap(*part_map);
   }
 }