Avoid creating FontCache for memory dump.

It is possible that a memory dump will be requested before the blink
font manager is set. This can result in attempting to create a fallback
font manager and ignoring the real one which may be set later. Avoid
this situation by ensuring that the memory dump request does not
implicitly cause a global FontCache to be created just to dump that it
is empty.

Bug: chromium:1140954
Cq-Include-Trybots: luci.chromium.try:win_chromium_dbg_ng
Change-Id: If29d830c66f85552663384898fbf3d29fb6d67e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490503
Commit-Queue: Ben Wagner <bungeman@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819842}

third_party/blink/renderer/platform/fonts/font_cache.cc

@@ -90,8 +90,8 @@ bool FontCache::lcd_text_enabled_ = false;
 bool FontCache::use_skia_font_fallback_ = false;
 #endif  // defined(OS_WIN)
 
-FontCache* FontCache::GetFontCache() {
-  return &FontGlobalContext::GetFontCache();
+FontCache* FontCache::GetFontCache(CreateIfNeeded create) {
+  return FontGlobalContext::GetFontCache(create);
 }
 
 FontCache::FontCache()

third_party/blink/renderer/platform/fonts/font_cache.h

@@ -91,6 +91,8 @@ enum class AlternateFontName {
   kLastResort
 };
 
+enum CreateIfNeeded { kDoNotCreate, kCreate };
+
 typedef HashMap<unsigned,
                 std::unique_ptr<FontPlatformData>,
                 WTF::IntHash<unsigned>,
@@ -113,7 +115,11 @@ class PLATFORM_EXPORT FontCache {
   USING_FAST_MALLOC(FontCache);
 
  public:
-  static FontCache* GetFontCache();
+  // FontCache initialisation on Windows depends on a global FontMgr being
+  // configured through a call from the browser process. CreateIfNeeded helps
+  // avoid early creation of a font cache when these globals have not yet
+  // been set.
+  static FontCache* GetFontCache(CreateIfNeeded = kCreate);
 
   void ReleaseFontData(const SimpleFontData*);
 

third_party/blink/renderer/platform/fonts/font_cache_memory_dump_provider.cc

@@ -18,8 +18,11 @@ bool FontCacheMemoryDumpProvider::OnMemoryDump(
     const base::trace_event::MemoryDumpArgs&,
     base::trace_event::ProcessMemoryDump* memory_dump) {
   DCHECK(IsMainThread());
-  FontCache::GetFontCache()->DumpFontPlatformDataCache(memory_dump);
-  FontCache::GetFontCache()->DumpShapeResultCache(memory_dump);
+  FontCache* cache = FontCache::GetFontCache(kDoNotCreate);
+  if (cache) {
+    cache->DumpFontPlatformDataCache(memory_dump);
+    cache->DumpShapeResultCache(memory_dump);
+  }
   return true;
 }
 

third_party/blink/renderer/platform/fonts/font_global_context.cc

@@ -90,12 +90,13 @@ IdentifiableToken FontGlobalContext::GetOrComputePostScriptNameDigest(
 }
 
 void FontGlobalContext::ClearMemory() {
-  if (!Get(kDoNotCreate))
+  FontGlobalContext* context = Get(kDoNotCreate);
+  if (!context)
     return;
 
-  GetFontCache().Invalidate();
-  Get()->typeface_digest_cache_.Clear();
-  Get()->postscript_name_digest_cache_.Clear();
+  context->font_cache_.Invalidate();
+  context->typeface_digest_cache_.Clear();
+  context->postscript_name_digest_cache_.Clear();
 }
 
 }  // namespace blink

third_party/blink/renderer/platform/fonts/font_global_context.h

@@ -21,8 +21,6 @@ class FontCache;
 class FontUniqueNameLookup;
 class HarfBuzzFontCache;
 
-enum CreateIfNeeded { kDoNotCreate, kCreate };
-
 // FontGlobalContext contains non-thread-safe, thread-specific data used for
 // font formatting.
 class PLATFORM_EXPORT FontGlobalContext {
@@ -31,7 +29,10 @@ class PLATFORM_EXPORT FontGlobalContext {
  public:
   static FontGlobalContext* Get(CreateIfNeeded = kCreate);
 
-  static inline FontCache& GetFontCache() { return Get()->font_cache_; }
+  static inline FontCache* GetFontCache(CreateIfNeeded create = kCreate) {
+    FontGlobalContext* context = Get(create);
+    return context ? &context->font_cache_ : nullptr;
+  }
 
   static HarfBuzzFontCache* GetHarfBuzzFontCache();