Replace use of std containers with WTF's equivalents in image.cc/h

Replace the use of std::map of std container with WTF::HashMap in
image.cc/h and use FloatSize instead of std::pair as HashMap's key.

Bug: 952716
Change-Id: I8476fd4710f71469806c6118e0dcfe37602bfe30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1599813Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Miyoung Shin <myid.shin@igalia.com>
Cr-Commit-Position: refs/heads/master@{#657666}

third_party/blink/renderer/platform/graphics/image.cc

@@ -375,12 +375,11 @@ DarkModeClassification Image::GetDarkModeClassification(
   // size, only the top left corner coordinates of the src_rect are used to
   // generate the key for caching and retrieving the classification.
   ClassificationKey key(src_rect.X(), src_rect.Y());
-  std::map<ClassificationKey, DarkModeClassification>::iterator result =
-      dark_mode_classifications_.find(key);
+  auto result = dark_mode_classifications_.find(key);
   if (result == dark_mode_classifications_.end())
     return DarkModeClassification::kNotClassified;
 
-  return result->second;
+  return result->value;
 }
 
 void Image::AddDarkModeClassification(
@@ -390,7 +389,7 @@ void Image::AddDarkModeClassification(
   DCHECK(GetDarkModeClassification(src_rect) ==
          DarkModeClassification::kNotClassified);
   ClassificationKey key(src_rect.X(), src_rect.Y());
-  dark_mode_classifications_[key] = dark_mode_classification;
+  dark_mode_classifications_.insert(key, dark_mode_classification);
 }
 
 bool Image::ShouldApplyDarkModeFilter(const FloatRect& src_rect) {

third_party/blink/renderer/platform/graphics/image.h

@@ -282,9 +282,8 @@ class PLATFORM_EXPORT Image : public ThreadSafeRefCounted<Image> {
       const FloatRect& src_rect,
       const DarkModeClassification dark_mode_classification);
 
-  typedef std::pair<float, float> ClassificationKey;
-  std::map<ClassificationKey, DarkModeClassification>
-      dark_mode_classifications_;
+  typedef FloatSize ClassificationKey;
+  HashMap<ClassificationKey, DarkModeClassification> dark_mode_classifications_;
 
  private:
   virtual DarkModeClassification ClassifyImageForDarkMode(