Get rid of "outrageous" default text styles for HTML renderer. (flutter#41822)

The CanvasKit renderer doesn't do this, so we should just remove the red text global style.

Author: eyebrowsoffire

lib/web_ui/lib/src/engine/global_styles.dart

@@ -18,13 +18,9 @@ void applyGlobalCssRulesToSheet(
   assert(styleElement.sheet != null);
   final DomCSSStyleSheet sheet = styleElement.sheet! as DomCSSStyleSheet;
 
-  // These are intentionally outrageous font parameters to make sure that the
-  // apps fully specify their text styles.
-  //
   // Fixes #115216 by ensuring that our parameters only affect the flt-scene-host children.
   sheet.insertRule('''
     $cssSelectorPrefix flt-scene-host {
-      color: red;
       font: $defaultCssFont;
     }
   ''', sheet.cssRules.length);

lib/web_ui/lib/src/engine/text/canvas_paragraph.dart

@@ -15,8 +15,6 @@ import 'paint_service.dart';
 import 'paragraph.dart';
 import 'word_breaker.dart';
 
-const ui.Color _defaultTextColor = ui.Color(0xFFFF0000);
-
 final String placeholderChar = String.fromCharCode(0xFFFC);
 
 /// A paragraph made up of a flat list of text spans and placeholders.
@@ -491,7 +489,7 @@ class RootStyleNode extends StyleNode {
   final EngineParagraphStyle paragraphStyle;
 
   @override
-  final ui.Color _color = _defaultTextColor;
+  ui.Color? get _color => null;
 
   @override
   ui.TextDecoration? get _decoration => null;

lib/web_ui/lib/src/engine/text/paint_service.dart

@@ -107,7 +107,10 @@ class TextPaintService {
     if (foreground != null) {
       paint = foreground as SurfacePaint;
     } else {
-      paint = (ui.Paint()..color = style.color!) as SurfacePaint;
+      paint = ui.Paint() as SurfacePaint;
+      if (style.color != null) {
+        paint.color = style.color!;
+      }
     }
 
     canvas.setCssFont(style.cssFontString, fragment.textDirection!);

lib/web_ui/test/engine/global_styles_test.dart

@@ -38,28 +38,6 @@ void testMain() {
     expect(hasFakeRule, isFalse);
   });
 
-  test('Attaches outrageous text styles to flt-scene-host', () {
-    final bool hasColorRed = hasCssRule(styleElement,
-        selector: 'flt-scene-host', declaration: 'color: red');
-
-    bool hasFont = false;
-    if (isSafari) {
-      // Safari expands the shorthand rules, so we check for all we've set (separately).
-      hasFont = hasCssRule(styleElement,
-              selector: 'flt-scene-host',
-              declaration: 'font-family: monospace') &&
-          hasCssRule(styleElement,
-              selector: 'flt-scene-host', declaration: 'font-size: 14px');
-    } else {
-      hasFont = hasCssRule(styleElement,
-          selector: 'flt-scene-host', declaration: 'font: $_kDefaultCssFont');
-    }
-
-    expect(hasColorRed, isTrue,
-        reason: 'Should make foreground color red within scene host.');
-    expect(hasFont, isTrue, reason: 'Should pass default css font.');
-  });
-
   test('Attaches styling to remove password reveal icons on Edge', () {
     // Check that style.sheet! contains input::-ms-reveal rule
     final bool hidesRevealIcons = hasCssRule(styleElement,

lib/web_ui/test/html/text/canvas_paragraph_builder_test.dart

@@ -514,7 +514,6 @@ String spanStyle({
   num? letterSpacing,
 }) {
   return <String>[
-    'color: rgb(255, 0, 0);',
     'font-size: ${fontSize}px;',
     if (fontWeight != null) 'font-weight: $fontWeight;',
     if (fontStyle != null) 'font-style: $fontStyle;',
@@ -529,7 +528,6 @@ String spanStyle({
 }
 
 TextStyle styleWithDefaults({
-  Color color = const Color(0xFFFF0000),
   String fontFamily = FlutterViewEmbedder.defaultFontFamily,
   double fontSize = FlutterViewEmbedder.defaultFontSize,
   FontWeight? fontWeight,
@@ -538,7 +536,6 @@ TextStyle styleWithDefaults({
   double? letterSpacing,
 }) {
   return TextStyle(
-    color: color,
     fontFamily: fontFamily,
     fontSize: fontSize,
     fontWeight: fontWeight,

lib/web_ui/test/html/text/layout_fragmenter_test.dart

@@ -10,7 +10,6 @@ import 'package:ui/ui.dart';
 import '../paragraph/helper.dart';
 
 final EngineTextStyle defaultStyle = EngineTextStyle.only(
-  color: const Color(0xFFFF0000),
   fontFamily: FlutterViewEmbedder.defaultFontFamily,
   fontSize: FlutterViewEmbedder.defaultFontSize,
 );