Add runtime flag for <script type="module">

Also exercise it in a very basic way in ScriptLoader (at the moment,
<script type="module"> is treated the same as <script>).

See intent-to-implement:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/uba6pMr-jec/tXdg6YYPBAAJ

BUG=594639

Review URL: https://codereview.chromium.org/1807293004

Cr-Commit-Position: refs/heads/master@{#382083}

4 files changed, 25 insertions, 0 deletions

diff --git a/third_party/WebKit/LayoutTests/fast/dom/HTMLScriptElement/module-script-expected.txt b/third_party/WebKit/LayoutTests/fast/dom/HTMLScriptElement/module-script-expected.txt
new file mode 100644
index 0000000..dfd9e5b
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/dom/HTMLScriptElement/module-script-expected.txt
@@ -0,0 +1,11 @@
+Test basic module execution.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+Module scripts should be executed...
+...and should ignore any 'language' attribute
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
diff --git a/third_party/WebKit/LayoutTests/fast/dom/HTMLScriptElement/module-script.html b/third_party/WebKit/LayoutTests/fast/dom/HTMLScriptElement/module-script.html
new file mode 100644
index 0000000..959ffaa
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/fast/dom/HTMLScriptElement/module-script.html
@@ -0,0 +1,11 @@
+<script src="../../../resources/js-test.js"></script>
+<script>
+description("Test basic module execution.");
+</script>
+<script type="module">
+debug("Module scripts should be executed...");
+</script>
+<script type="module" language="nonsense">
+debug("...and should ignore any 'language' attribute");
+</script>
+
diff --git a/third_party/WebKit/Source/core/dom/ScriptLoader.cpp b/third_party/WebKit/Source/core/dom/ScriptLoader.cpp
index b33f34f..7197892 100644
--- a/third_party/WebKit/Source/core/dom/ScriptLoader.cpp
+++ b/third_party/WebKit/Source/core/dom/ScriptLoader.cpp
@@ -175,6 +175,8 @@ bool ScriptLoader::isScriptTypeSupported(LegacyTypeSupport supportLegacyTypes) c
         type = "text/" + language.lower();
         if (MIMETypeRegistry::isSupportedJavaScriptMIMEType(type) || isLegacySupportedJavaScriptLanguage(language))
             return true;
+    } else if (RuntimeEnabledFeatures::moduleScriptsEnabled() && type == "module") {
+        return true;
     } else if (MIMETypeRegistry::isSupportedJavaScriptMIMEType(type.stripWhiteSpace()) || (supportLegacyTypes == AllowLegacyTypeInTypeAttribute && isLegacySupportedJavaScriptLanguage(type))) {
         return true;
     }
diff --git a/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in b/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
index b7c2bcf..2f54c21 100644
--- a/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
+++ b/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
@@ -121,6 +121,7 @@ MediaSourceExperimental status=experimental
 MediaStreamSpeech status=experimental
 MemoryInfoInWorkers status=experimental
 MobileLayoutTheme
+ModuleScripts status=test
 NavigatorConnect status=experimental
 NavigatorContentUtils
 WebNFC status=experimental