Make WebCore::WebVTTParser testable

https://bugs.webkit.org/show_bug.cgi?id=270526
<rdar://124077524>

Reviewed by Alex Christensen.

* Source/WebCore/WebCore.xcodeproj/project.pbxproj:
- Make BufferedLineReader.h and WebVTTParser.h private headers.
* Source/WebCore/html/track/VTTRegion.h:
- Export WebCore::VTTRegion class.
* Source/WebCore/html/track/WebVTTParser.h:
- Export WebCore::WebVTTParser class.
(WebCore::WebVTTParser::WebVTTParser):
- Delete unused default constructor.

Canonical link: https://commits.webkit.org/275743@main

Source/WebCore/WebCore.xcodeproj/project.pbxproj

@@ -2515,7 +2515,7 @@
 		5CE19CF728D9020100A4571E /* WebCorePersistentCoders.h in Headers */ = {isa = PBXBuildFile; fileRef = 5CE19CF328D8FB3700A4571E /* WebCorePersistentCoders.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		5CEEE4361F5F8F210014A5F5 /* RectEdges.h in Headers */ = {isa = PBXBuildFile; fileRef = 5C97A3361F5F7A6500105207 /* RectEdges.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		5CFC9C842B71AE1800F8D289 /* SerializedPlatformDataCueValue.mm in Sources */ = {isa = PBXBuildFile; fileRef = 5CFC9C822B71ABF200F8D289 /* SerializedPlatformDataCueValue.mm */; };
-		5D21A80313ECE5DF00BB7064 /* WebVTTParser.h in Headers */ = {isa = PBXBuildFile; fileRef = 5D21A80113ECE5DF00BB7064 /* WebVTTParser.h */; };
+		5D21A80313ECE5DF00BB7064 /* WebVTTParser.h in Headers */ = {isa = PBXBuildFile; fileRef = 5D21A80113ECE5DF00BB7064 /* WebVTTParser.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		5D5975B319635F1100D00878 /* SystemVersion.h in Headers */ = {isa = PBXBuildFile; fileRef = 5D5975B119635F1100D00878 /* SystemVersion.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		5DA5E0FD102B953800088CF9 /* JSWebSocket.h in Headers */ = {isa = PBXBuildFile; fileRef = 5DA5E0FB102B953800088CF9 /* JSWebSocket.h */; };
 		5DB1BC6A10715A6400EFAA49 /* TransformSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 5DB1BC6810715A6400EFAA49 /* TransformSource.h */; };
@@ -2885,7 +2885,7 @@
 		7A22732120C9FAFE00DB1DEF /* WebKitNSImageExtras.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A22731F20C9F9DA00DB1DEF /* WebKitNSImageExtras.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		7A293F5229945A430033D744 /* FontCustomPlatformData.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A293F5129945A100033D744 /* FontCustomPlatformData.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		7A29F57218C69514004D0F81 /* OutOfBandTextTrackPrivateAVF.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A29F57118C69514004D0F81 /* OutOfBandTextTrackPrivateAVF.h */; };
-		7A45033018DB717200377B34 /* BufferedLineReader.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A45032E18DB717200377B34 /* BufferedLineReader.h */; };
+		7A45033018DB717200377B34 /* BufferedLineReader.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A45032E18DB717200377B34 /* BufferedLineReader.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		7A54858014E02D51006AE05A /* InspectorHistory.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A54857E14E02D51006AE05A /* InspectorHistory.h */; };
 		7A54881714E432A1006AE05A /* DOMPatchSupport.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A54881514E432A1006AE05A /* DOMPatchSupport.h */; };
 		7A5515F5191830A3009687D2 /* YouTubePluginReplacement.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A5515F3191830A3009687D2 /* YouTubePluginReplacement.h */; settings = {ATTRIBUTES = (Private, ); }; };

Source/WebCore/html/track/VTTRegion.h

@@ -44,7 +44,7 @@ class HTMLDivElement;
 class VTTCueBox;
 class VTTScanner;
 
-class VTTRegion final : public RefCounted<VTTRegion>, public ContextDestructionObserver {
+class WEBCORE_EXPORT VTTRegion final : public RefCounted<VTTRegion>, public ContextDestructionObserver {
 public:
     static Ref<VTTRegion> create(ScriptExecutionContext& context)
     {

Source/WebCore/html/track/WebVTTParser.h

@@ -96,7 +96,7 @@ class WebVTTCueData final : public RefCounted<WebVTTCueData> {
     String m_settings;
 };
 
-class WebVTTParser final {
+class WEBCORE_EXPORT WebVTTParser final {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     enum ParseState {
@@ -111,6 +111,7 @@ class WebVTTParser final {
         Finished
     };
 
+    WebVTTParser() = delete;
     WebVTTParser(WebVTTParserClient&, Document&);
 
     static inline bool isRecognizedTag(const AtomString& tagName)