Bug 1913382 - count the rate of SVG elements with surprising children r=hsivonen

Differential Revision: https://phabricator.services.mozilla.com/D219290

parser/html/metrics.yaml

@@ -0,0 +1,24 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Adding a new metric? We have docs for that!
+# https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/new_definitions_file.html
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - 'Core :: DOM: HTML Parser'
+
+parsing:
+  svg_unusual_pcdata:
+    type: rate
+    description: |
+      The rate of svg elements that have child elements during parsing, where their HTML counterpart would not have children.
+    notification_emails:
+      - seceng-telemetry@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1913382
+    data_reviews:
+      - https://phabricator.services.mozilla.com/D219290#7592177
+    expires: 136

parser/html/nsHtml5TreeBuilderCppSupplement.h

@@ -13,6 +13,7 @@
 #include "mozilla/dom/FetchPriority.h"
 #include "mozilla/dom/ShadowRoot.h"
 #include "mozilla/dom/ShadowRootBinding.h"
+#include "mozilla/glean/GleanMetrics.h"
 #include "mozilla/CheckedInt.h"
 #include "mozilla/Likely.h"
 #include "mozilla/StaticPrefs_dom.h"
@@ -1139,6 +1140,8 @@ void nsHtml5TreeBuilder::markMalformedIfScript(nsIContentHandle* aElement) {
 
 void nsHtml5TreeBuilder::start(bool fragment) {
   mCurrentHtmlScriptCannotDocumentWriteOrBlock = false;
+  mozilla::glean::parsing::svg_unusual_pcdata.AddToDenominator(1);
+
 #ifdef DEBUG
   mActive = true;
 #endif
@@ -1206,6 +1209,19 @@ void nsHtml5TreeBuilder::elementPushed(int32_t aNamespace, nsAtom* aName,
    * table elements shouldn't be used as surrogate parents for user experience
    * reasons.
    */
+
+  if (isInSVGOddPCData) {
+    // We are seeing an element that has children, which could not have child
+    // elements in HTML, i.e., is parsed as PCDATA in SVG but CDATA in HTML.
+    mozilla::glean::parsing::svg_unusual_pcdata.AddToNumerator(1);
+  }
+  if ((aName == nsGkAtoms::style) || (aName == nsGkAtoms::xmp) ||
+      (aName == nsGkAtoms::iframe) || (aName == nsGkAtoms::noembed) ||
+      (aName == nsGkAtoms::noframes) || (aName == nsGkAtoms::noscript) ||
+      (aName == nsGkAtoms::script)) {
+    isInSVGOddPCData++;
+  }
+
   if (aNamespace != kNameSpaceID_XHTML) {
     return;
   }
@@ -1255,6 +1271,14 @@ void nsHtml5TreeBuilder::elementPopped(int32_t aNamespace, nsAtom* aName,
   if (aNamespace == kNameSpaceID_MathML) {
     return;
   }
+  if (aNamespace == kNameSpaceID_SVG) {
+    if ((aName == nsGkAtoms::style) || (aName == nsGkAtoms::xmp) ||
+        (aName == nsGkAtoms::iframe) || (aName == nsGkAtoms::noembed) ||
+        (aName == nsGkAtoms::noframes) || (aName == nsGkAtoms::noscript) ||
+        (aName == nsGkAtoms::script)) {
+      isInSVGOddPCData--;
+    }
+  }
   // we now have only SVG and HTML
   if (aName == nsGkAtoms::script) {
     if (mPreventScriptExecution) {

parser/html/nsHtml5TreeBuilderHSupplement.h

@@ -23,6 +23,7 @@ int32_t mHandlesUsed;
 nsTArray<mozilla::UniquePtr<nsIContent*[]>> mOldHandles;
 nsHtml5TreeOpStage* mSpeculativeLoadStage;
 nsresult mBroken;
+int32_t isInSVGOddPCData = 0;
 // Controls whether the current HTML script goes through the more complex
 // path that accommodates the possibility of the script becoming a
 // parser-blocking script and the possibility of the script inserting

toolkit/components/glean/metrics_index.py

@@ -28,6 +28,7 @@ gecko_metrics = [
     "dom/security/metrics.yaml",
     "dom/webauthn/metrics.yaml",
     "gfx/metrics.yaml",
+    "parser/html/metrics.yaml",
     "image/decoders/metrics.yaml",
     "js/xpconnect/metrics.yaml",
     "layout/base/metrics.yaml",