Remove dead exception for MediaList.appendMedium

MediaList.appendMedium was able to throw an exception, but
MediaQuerySet::Add() always returned true, making it impossible for that
exception to be thrown. This matched the spec, as |appendMedium| cannot
throw an exception. Remove the dead code surrounding the possible
exception, and make MediaQuerySet::Add() return false if the medium is
not added. Also remove the TODO as deleteMedium can throw an exception
per the spec.

Change-Id: I32c1b7b3ac90812ce036273e9c1c56f6d65c0af2
Reviewed-on: https://chromium-review.googlesource.com/993398
Commit-Queue: Chris Nardi <cnardi@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547909}

third_party/WebKit/Source/core/css/MediaList.cpp

@@ -82,7 +82,7 @@ bool MediaQuerySet::Add(const String& query_string) {
 
   // Only continue if exactly one media query is found, as described above.
   if (result->queries_.size() != 1)
-    return true;
+    return false;
 
   std::unique_ptr<MediaQuery> new_query = std::move(result->queries_[0]);
   // TODO(keishi) Changed DCHECK to CHECK for crbug.com/699269 diagnosis
@@ -93,7 +93,7 @@ bool MediaQuerySet::Add(const String& query_string) {
   for (size_t i = 0; i < queries_.size(); ++i) {
     MediaQuery& query = *queries_[i];
     if (query == *new_query)
-      return true;
+      return false;
   }
 
   queries_.push_back(std::move(new_query));
@@ -192,17 +192,12 @@ void MediaList::deleteMedium(const String& medium,
     parent_style_sheet_->DidMutate();
 }
 
-void MediaList::appendMedium(const String& medium,
-                             ExceptionState& exception_state) {
+void MediaList::appendMedium(const String& medium) {
   CSSStyleSheet::RuleMutationScope mutation_scope(parent_rule_);
 
-  bool success = media_queries_->Add(medium);
-  if (!success) {
-    exception_state.ThrowDOMException(
-        kInvalidCharacterError,
-        "The value provided ('" + medium + "') is not a valid medium.");
+  bool added = media_queries_->Add(medium);
+  if (!added)
     return;
-  }
 
   if (parent_style_sheet_)
     parent_style_sheet_->DidMutate();

third_party/WebKit/Source/core/css/MediaList.h

@@ -86,7 +86,7 @@ class MediaList final : public ScriptWrappable {
   unsigned length() const { return media_queries_->QueryVector().size(); }
   String item(unsigned index) const;
   void deleteMedium(const String& old_medium, ExceptionState&);
-  void appendMedium(const String& new_medium, ExceptionState&);
+  void appendMedium(const String& new_medium);
 
   String mediaText() const { return media_queries_->MediaText(); }
   void setMediaText(const String&);

third_party/WebKit/Source/core/css/MediaList.idl

@@ -32,7 +32,6 @@
     stringifier attribute [TreatNullAs=EmptyString] DOMString mediaText;
     readonly attribute unsigned long length;
     [Measure] getter DOMString? item(unsigned long index);
-    // TODO(foolip): appendMedium() and deleteMedium() should never throw.
-    [RaisesException] void appendMedium(DOMString medium);
+    void appendMedium(DOMString medium);
     [RaisesException] void deleteMedium(DOMString medium);
 };