[Fallback Icons] Refactor FallbackIconService to be a BrowserContext-level singleton

components/favicon_base/fallback_icon_service.cc

Index: components/favicon_base/fallback_icon_service.cc
diff --git a/components/favicon_base/fallback_icon_service.cc b/components/favicon_base/fallback_icon_service.cc
index adce72e105f6a1fce671c62fb27dabcecfb0ef87..3a41be5a8176a0f6c9ec4c5955e68b118c2d655d 100644
--- a/components/favicon_base/fallback_icon_service.cc
+++ b/components/favicon_base/fallback_icon_service.cc
@@ -8,6 +8,7 @@
 
 #include "base/i18n/case_conversion.h"
 #include "base/strings/utf_string_conversions.h"
+#include "components/favicon/core/browser/fallback_icon_client.h"
 #include "components/favicon_base/fallback_icon_style.h"
 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
 #include "third_party/skia/include/core/SkPaint.h"
@@ -38,8 +39,8 @@ base::string16 GetFallbackIconText(const GURL& url) {
 }  // namespace
 
 FallbackIconService::FallbackIconService(
-    const std::vector<std::string>& font_list)
-  : font_list_(font_list) {
+    FallbackIconClient* fallback_icon_client)
+    : fallback_icon_client_(fallback_icon_client) {
 }
 
 FallbackIconService::~FallbackIconService() {
@@ -88,7 +89,8 @@ void FallbackIconService::DrawFallbackIcon(const GURL& icon_url,
   // TODO(huangs): See how expensive gfx::FontList() is, and possibly cache.
   canvas->DrawStringRectWithFlags(
       icon_text,
-      gfx::FontList(font_list_, gfx::Font::NORMAL, font_size),
+      gfx::FontList(fallback_icon_client_->GetFontList(), gfx::Font::NORMAL,
+                    font_size),
       style.text_color,
       gfx::Rect(kOffsetX, kOffsetY, size, size),
       gfx::Canvas::TEXT_ALIGN_CENTER);