Bug 1446614 - textPath should not render if the path it uses is invalid r=dholbert

layout/reftests/svg/reftest.list

@@ -475,6 +475,7 @@ fuzzy(16,3) == text-stroke-scaling-02b.html text-stroke-scaling-02-ref.html # an
 fuzzy-if(skiaContent,1,610) == textPath-03.svg pass.svg
 == textPath-04.svg pass.svg
 == textPath-05.html pass.svg
+== textPath-06.svg pass.svg
 == textPath-line-01.svg textPath-line-01-ref.svg
 
 == text-white-space-01.svg text-white-space-01-ref.svg

layout/reftests/svg/textPath-06.svg

@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <path id="path" d="" />
+  </defs>
+
+  <rect fill="lime" width="100%" height="100%"/>
+
+  <text y="50" font-size="50" fill="red" >
+    <textPath path="">Empty paths should be invisible</textPath>
+  </text>
+
+  <text y="100" font-size="50" fill="red" >
+    <textPath href="#path">Empty paths should be invisible</textPath>
+  </text>
+
+  <text y="150" font-size="50" fill="red" >
+    <textPath>No path at all should be invisible too</textPath>
+  </text>
+</svg>

layout/svg/SVGTextFrame.cpp

@@ -5083,7 +5083,12 @@ SVGTextFrame::DoTextPathLayout()
     // Get the path itself.
     RefPtr<Path> path = GetTextPath(textPathFrame);
     if (!path) {
+      uint32_t start = it.TextElementCharIndex();
       it.AdvancePastCurrentTextPathFrame();
+      uint32_t end = it.TextElementCharIndex();
+      for (uint32_t i = start; i < end; i++) {
+        mPositions[i].mHidden = true;
+      }
       continue;
     }