Neuter the "screen scale factor" computation for SVG <text>

This removes the PaintLayer-factor and DSF from the "screen scale factor",
leaving only the transform to the <svg> root and the "content transform" (used
by <pattern>, <mask> and <clipPath>.)

BUG=664961

Review-Url: https://codereview.chromium.org/2492013004
Cr-Commit-Position: refs/heads/master@{#435599}

third_party/WebKit/LayoutTests/platform/mac/svg/custom/masking-clipping-hidpi-expected.txt

@@ -5,18 +5,18 @@ layer at (0,0) size 800x600
     LayoutSVGHiddenContainer {defs} at (0,0) size 0x0
       LayoutSVGResourceMasker {mask} [id="textMask"] [maskUnits=objectBoundingBox] [maskContentUnits=userSpaceOnUse]
         LayoutSVGRect {rect} at (0,0) size 800x600 [fill={[type=SOLID] [color=#FFFFFF]}] [x=0.00] [y=0.00] [width=800.00] [height=600.00]
-        LayoutSVGText {text} at (0,-2.50) size 164.86x18.50 contains 1 chunk(s)
-          LayoutSVGInlineText {#text} at (0,-2.50) size 164.86x18.50
+        LayoutSVGText {text} at (0,-2) size 164.86x18 contains 1 chunk(s)
+          LayoutSVGInlineText {#text} at (0,-2) size 164.86x18
             chunk 1 text run 1 at (0.00,12.00) startOffset 0 endOffset 26 width 164.87: "This text should be sharp."
     LayoutSVGRect {rect} at (0,0) size 200x100 [fill={[type=SOLID] [color=#000000]}] [x=0.00] [y=0.00] [width=200.00] [height=100.00]
     LayoutSVGRect {rect} at (0,0) size 200x100 [fill={[type=SOLID] [color=#FFFFFF]}] [x=0.00] [y=0.00] [width=200.00] [height=100.00]
-      [masker="textMask"] LayoutSVGResourceMasker {mask} at (0,-2.50) size 220x112.50
+      [masker="textMask"] LayoutSVGResourceMasker {mask} at (0,-2) size 220x112
     LayoutSVGHiddenContainer {defs} at (0,0) size 0x0
       LayoutSVGResourceLinearGradient {linearGradient} [id="blackGradient"] [gradientUnits=objectBoundingBox] [start=(0,0)] [end=(1,0)]
         LayoutSVGGradientStop {stop} [offset=0.00] [color=#000000]
         LayoutSVGGradientStop {stop} [offset=1.00] [color=#000000]
-    LayoutSVGText {text} at (0,21.50) size 291.03x18.50 contains 1 chunk(s)
-      LayoutSVGInlineText {#text} at (0,21.50) size 291.03x18.50
+    LayoutSVGText {text} at (0,22) size 291.03x18 contains 1 chunk(s)
+      LayoutSVGInlineText {#text} at (0,22) size 291.03x18
         chunk 1 text run 1 at (0.00,36.00) startOffset 0 endOffset 47 width 291.04: "This text and the circles should also be sharp."
     LayoutSVGHiddenContainer {defs} at (0,0) size 0x0
       LayoutSVGResourceClipper {clipPath} [id="circleClipPath"] [clipPathUnits=objectBoundingBox]

third_party/WebKit/Source/core/layout/svg/SVGLayoutSupport.cpp

@@ -520,7 +520,7 @@ SubtreeContentTransformScope::~SubtreeContentTransformScope() {
   m_savedContentTransformation.copyTransformTo(s_currentContentTransformation);
 }
 
-AffineTransform SVGLayoutSupport::deprecatedCalculateTransformToLayer(
+float SVGLayoutSupport::calculateScreenFontSizeScalingFactor(
     const LayoutObject* layoutObject) {
   AffineTransform transform;
   while (layoutObject) {
@@ -529,44 +529,10 @@ AffineTransform SVGLayoutSupport::deprecatedCalculateTransformToLayer(
       break;
     layoutObject = layoutObject->parent();
   }
-
-  // Continue walking up the layer tree, accumulating CSS transforms.
-  // FIXME: this queries layer compositing state - which is not
-  // supported during layout. Hence, the result may not include all CSS
-  // transforms.
-  PaintLayer* layer = layoutObject ? layoutObject->enclosingLayer() : 0;
-  while (layer && layer->isAllowedToQueryCompositingState()) {
-    // We can stop at compositing layers, to match the backing resolution.
-    // FIXME: should we be computing the transform to the nearest composited
-    // layer, or the nearest composited layer that does not paint into its
-    // ancestor? I think this is the nearest composited ancestor since we will
-    // inherit its transforms in the composited layer tree.
-    if (layer->compositingState() != NotComposited)
-      break;
-
-    if (TransformationMatrix* layerTransform = layer->transform())
-      transform = layerTransform->toAffineTransform() * transform;
-
-    layer = layer->parent();
-  }
-
-  return transform;
-}
-
-float SVGLayoutSupport::calculateScreenFontSizeScalingFactor(
-    const LayoutObject* layoutObject) {
-  ASSERT(layoutObject);
-
-  // FIXME: trying to compute a device space transform at record time is wrong.
-  // All clients should be updated to avoid relying on this information, and the
-  // method should be removed.
-  AffineTransform ctm =
-      deprecatedCalculateTransformToLayer(layoutObject) *
-      SubtreeContentTransformScope::currentContentTransformation();
-  ctm.scale(
-      layoutObject->document().frameHost()->deviceScaleFactorDeprecated());
-
-  return clampTo<float>(sqrt((ctm.xScaleSquared() + ctm.yScaleSquared()) / 2));
+  transform.multiply(
+      SubtreeContentTransformScope::currentContentTransformation());
+  return clampTo<float>(
+      sqrt((transform.xScaleSquared() + transform.yScaleSquared()) / 2));
 }
 
 static inline bool compareCandidateDistance(const SearchCandidate& r1,

third_party/WebKit/Source/core/layout/svg/SVGLayoutSupport.h

@@ -145,8 +145,6 @@ class CORE_EXPORT SVGLayoutSupport {
   static bool computeHasNonIsolatedBlendingDescendants(const LayoutObjectType*);
   static bool isIsolationRequired(const LayoutObject*);
 
-  static AffineTransform deprecatedCalculateTransformToLayer(
-      const LayoutObject*);
   static float calculateScreenFontSizeScalingFactor(const LayoutObject*);
 
   static LayoutObject* findClosestLayoutSVGText(LayoutObject*,