Reduce Canvas FontCache size on low end devices

third_party/WebKit/Source/core/html/canvas/CanvasFontCache.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/html/canvas/CanvasFontCache.h"
 
 #include "core/css/parser/CSSParser.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/Document.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/wtf/PtrUtil.h"
 #include "public/platform/Platform.h"
 
 namespace {
 
 const unsigned CanvasFontCacheMaxFonts = 50;
+const unsigned CanvasFontCacheMaxFontsLowEnd = 5;
 const unsigned CanvasFontCacheHardMaxFonts = 250;
+const unsigned CanvasFontCacheHardMaxFontsLowEnd = 20;
 const unsigned CanvasFontCacheHiddenMaxFonts = 1;
 const int defaultFontSize = 10;
 const char defaultFontFamily[] = "sans-serif";
 }
 
 namespace blink {
 
 CanvasFontCache::CanvasFontCache(Document& document)
     : document_(&document), pruning_scheduled_(false) {
   FontFamily font_family;
   font_family.SetFamily(defaultFontFamily);
   FontDescription default_font_description;
   default_font_description.SetFamily(font_family);
   default_font_description.SetSpecifiedSize(defaultFontSize);
   default_font_description.SetComputedSize(defaultFontSize);
   default_font_style_ = ComputedStyle::Create();
   default_font_style_->SetFontDescription(default_font_description);
   default_font_style_->GetFont().Update(
       default_font_style_->GetFont().GetFontSelector());
 }
 
 CanvasFontCache::~CanvasFontCache() {
   main_cache_purge_preventer_.reset();
   if (pruning_scheduled_) {
     Platform::Current()->CurrentThread()->RemoveTaskObserver(this);
   }
 }
 
 unsigned CanvasFontCache::MaxFonts() {
-  return CanvasFontCacheMaxFonts;
+  return MemoryCoordinator::IsLowEndDevice() ? CanvasFontCacheMaxFontsLowEnd
+                                             : CanvasFontCacheMaxFonts;
 }
 
 unsigned CanvasFontCache::HardMaxFonts() {
   return document_->hidden() ? CanvasFontCacheHiddenMaxFonts
-                             : CanvasFontCacheHardMaxFonts;
+                             : (MemoryCoordinator::IsLowEndDevice()
+                                    ? CanvasFontCacheHardMaxFontsLowEnd
+                                    : CanvasFontCacheHardMaxFonts);
 }
 
 bool CanvasFontCache::GetFontUsingDefaultStyle(const String& font_string,
                                                Font& resolved_font) {
   HashMap<String, Font>::iterator i =
       fonts_resolved_using_default_style_.find(font_string);
   if (i != fonts_resolved_using_default_style_.end()) {
     DCHECK(font_lru_list_.Contains(font_string));
     font_lru_list_.erase(font_string);
     font_lru_list_.insert(font_string);
@@ skipping 84 matching lines @@
   font_lru_list_.clear();
   fonts_resolved_using_default_style_.clear();
 }
 
 DEFINE_TRACE(CanvasFontCache) {
   visitor->Trace(fetched_fonts_);
   visitor->Trace(document_);
 }
 
 }  // namespace blink