clean up image policy code

1. use ResourceResponse::ExpectedContentLength to get image file size.
2. merge image policy violation check into one place.
    Note: ValidateImagePolicies will later be called through the
    pipeline described in here:
https://docs.google.com/document/d/1B_GnzEItUXsUUQXtB1zMiiov86_U1BCFo1F8g5F_yOY
    to unload unoptimized images as early as possible.


Bug:910195

Change-Id: Iab2fc2fee4f2963c308ca1cc585259021a86b3f2
Reviewed-on: https://chromium-review.googlesource.com/c/1355330
Commit-Queue: Luna Lu <loonybear@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612362}

third_party/blink/renderer/core/layout/layout_image.cc

@@ -53,7 +53,6 @@ namespace {
 constexpr float kmax_oversize_ratio = 2.0f;
 
 bool CheckForOptimizedImagePolicy(const Document& document,
-                                  LayoutImage* layout_image,
                                   ImageResourceContent* new_image) {
   // Render the image as a placeholder image if the document does not have the
   // 'legacy-image-formats' feature enabled, and the image is not one of the
@@ -273,12 +272,8 @@ void LayoutImage::ImageNotifyFinished(ImageResourceContent* new_image) {
   InvalidateBackgroundObscurationStatus();
 
   // Check for optimized image policies.
-  is_legacy_format_or_unoptimized_image_ =
-      CheckForOptimizedImagePolicy(GetDocument(), this, new_image);
-  if (auto* image_element = ToHTMLImageElementOrNull(GetNode())) {
-    is_oversized_image_ =
-        CheckForOversizedImagesPolicy(GetDocument(), new_image, this);
-  }
+  if (IsHTMLImageElement(GetNode()))
+    ValidateImagePolicies();
 
   if (new_image == image_resource_->CachedImage()) {
     // tell any potential compositing layers
@@ -491,15 +486,22 @@ bool LayoutImage::IsImagePolicyViolated() const {
   return is_oversized_image_ || is_legacy_format_or_unoptimized_image_;
 }
 
+void LayoutImage::ValidateImagePolicies() {
+  if (image_resource_ && image_resource_->CachedImage()) {
+    is_oversized_image_ = CheckForOversizedImagesPolicy(
+        GetDocument(), image_resource_->CachedImage(), this);
+    is_legacy_format_or_unoptimized_image_ = CheckForOptimizedImagePolicy(
+        GetDocument(), image_resource_->CachedImage());
+  }
+}
+
 void LayoutImage::UpdateAfterLayout() {
   LayoutBox::UpdateAfterLayout();
   Node* node = GetNode();
+
   if (auto* image_element = ToHTMLImageElementOrNull(node)) {
-    if (image_resource_ && image_resource_->CachedImage()) {
-      // Check for optimized image policies.
-      is_oversized_image_ = CheckForOversizedImagesPolicy(
-          GetDocument(), image_resource_->CachedImage(), this);
-    }
+    // Check for optimized image policies.
+    ValidateImagePolicies();
 
     // Report violation of unsized-media policy.
     if (image_element->IsDefaultIntrinsicSize())

third_party/blink/renderer/core/layout/layout_image.h

@@ -142,6 +142,8 @@ class CORE_EXPORT LayoutImage : public LayoutReplaced {
   FloatSize ImageSizeOverriddenByIntrinsicSize(float multiplier) const;
   IntSize GetOverriddenIntrinsicSize() const;
 
+  void ValidateImagePolicies();
+
   // This member wraps the associated decoded image.
   //
   // This field is set using setImageResource above which can be called in

third_party/blink/renderer/core/loader/resource/image_resource_content.cc

@@ -510,7 +510,7 @@ bool ImageResourceContent::IsAcceptableCompressionRatio() {
   if (!pixels)
     return true;
   DCHECK(image_);
-  double resource_length = image_->Data() ? image_->Data()->size() : 0;
+  double resource_length = GetResponse().ExpectedContentLength();
   // Allow no more than 10 bits per compressed pixel
   return (resource_length - 1024) / pixels <= 0.5;
 }