GCC: rename Color getter to LineColor in TextDecorationInfo to avoid clashing with Color type

GCC fails to compile the Color getter in TextDecorationInfo, as it
gets confused by different declarations in different namespaces:
../../third_party/blink/renderer/core/paint/text_decoration_info.h: At global scope:
../../third_party/blink/renderer/core/paint/text_decoration_info.h:76:9: error: declaration of ‘blink::Color blink::TextDecorationInfo::Color() const’ changes meaning of ‘Color’ [-fpermissive]
   76 |   Color Color() const;
      |         ^~~~~

To avoid that, we rename the getter to be LineColor.

Bug: 819294
Change-Id: I5b1a0d8a9c4580029ba8148281f9a3a514a88b62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339487
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795934}

third_party/blink/renderer/core/paint/applied_decoration_painter.cc

@@ -10,7 +10,7 @@ namespace blink {
 
 void AppliedDecorationPainter::Paint() {
   context_.SetStrokeStyle(decoration_info_.StrokeStyle());
-  context_.SetStrokeColor(decoration_info_.Color());
+  context_.SetStrokeColor(decoration_info_.LineColor());
 
   switch (decoration_info_.DecorationStyle()) {
     case ETextDecorationStyle::kWavy:

third_party/blink/renderer/core/paint/text_decoration_info.cc

@@ -200,7 +200,7 @@ ETextDecorationStyle TextDecorationInfo::DecorationStyle() const {
   return style_.AppliedTextDecorations()[decoration_index_].Style();
 }
 
-Color TextDecorationInfo::Color() const {
+Color TextDecorationInfo::LineColor() const {
   return style_.AppliedTextDecorations()[decoration_index_].GetColor();
 }
 

third_party/blink/renderer/core/paint/text_decoration_info.h

@@ -73,7 +73,7 @@ class CORE_EXPORT TextDecorationInfo {
 
   // SetDecorationIndex must be called before using these methods.
   ETextDecorationStyle DecorationStyle() const;
-  Color Color() const;
+  Color LineColor() const;
   float ResolvedThickness() const {
     return applied_decorations_thickness_[decoration_index_];
   }