Bug 1488300 - Kick off external SVG resource loading from DidSetComputedStyle. r=dholbert

Differential Revision: https://phabricator.services.mozilla.com/D4901

--HG--
extra : moz-landing-system : lando

layout/generic/nsFrame.cpp

@@ -1203,6 +1203,18 @@ nsFrame::DidSetComputedStyle(ComputedStyle* aOldComputedStyle)
     }
   }
 
+  // SVGObserverUtils::GetEffectProperties() asserts that we only invoke it with
+  // the first continuation so we need to check that in advance. Continuing text
+  // frame doesn't initialize its continuation pointer before reaching here for
+  // the first time, so we have to exclude text frames. This doesn't affect
+  // correctness because text nodes themselves shouldn't have effects applied.
+  if (!IsTextFrame() && !GetPrevContinuation()) {
+    // Kick off loading of external SVG resources referenced from properties if
+    // any. This currently includes filter, clip-path, and mask. We don't care
+    // about the return value. We only want its side effect.
+    Unused << SVGObserverUtils::GetEffectProperties(this);
+  }
+
   // If the page contains markup that overrides text direction, and
   // does not contain any characters that would activate the Unicode
   // bidi algorithm, we need to call |SetBidiEnabled| on the pres

testing/web-platform/meta/MANIFEST.json

@@ -544749,7 +544749,7 @@
    "reftest"
   ],
   "css/css-masking/mask-image/mask-image-url-remote-mask.html": [
-   "cfa3a6166cdcb41b2feaab2ffd5c087a568771f5",
+   "f3f2eefaa92df83296379efd861b39e2ab65f78e",
    "reftest"
   ],
   "css/css-masking/mask-image/reference/mask-image-ref.html": [
@@ -544765,7 +544765,7 @@
    "support"
   ],
   "css/css-masking/mask-image/support/mask.svg": [
-   "30e601c87c32a08912e261dab22734033df1ef8e",
+   "cab55923d32ddb9525cb81a12d8035b1bf51bb4c",
    "support"
   ],
   "css/css-masking/parsing/clip-invalid.html": [

testing/web-platform/tests/css/css-masking/mask-image/mask-image-url-remote-mask.html

@@ -26,8 +26,3 @@
 </style>
 <p>The test passes if there is a green square and no red below.</p>
 <div id="back"></div><div id="front"></div>
-<svg>
-  <!-- mask-image doesn't block onload, so we use an empty g here to
-       force mask.svg to load before onload. -->
-  <use href="support/mask.svg#empty"/>
-</svg>

testing/web-platform/tests/css/css-masking/mask-image/support/mask.svg

@@ -2,5 +2,4 @@
   <mask id="mask">
     <rect x="50" y="50" width="100" height="100" fill="white"/>
   </mask>
-  <g id="empty"/>
 </svg>