Fix resolution of 'auto' in SVGLengthContext::ResolveLengthPair

If one of the Lengths was 'auto' while the other was a percentage or
calc(...), the 'auto' Length would resolve to the corresponding viewport
dimension (i.e like if it was 100%) rather than 0.

Fixed: 1131324
Change-Id: Iec4e406d74b29551f417ab32caf3ef6cc627909b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426483Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#809844}

third_party/blink/renderer/core/svg/svg_length_context.cc

@@ -202,9 +202,16 @@ FloatPoint SVGLengthContext::ResolveLengthPair(
     const Length& y_length,
     const ComputedStyle& style) const {
   FloatSize viewport_size;
-  if (x_length.IsPercentOrCalc() || y_length.IsPercentOrCalc())
+  if (x_length.IsPercentOrCalc() || y_length.IsPercentOrCalc()) {
     DetermineViewport(viewport_size);
-
+    // If either |x_length| or |y_length| is 'auto', set that viewport dimension
+    // to zero so that the corresponding Length resolves to zero. This matches
+    // the behavior of ValueForLength() below.
+    if (x_length.IsAuto())
+      viewport_size.SetWidth(0);
+    else if (y_length.IsAuto())
+      viewport_size.SetHeight(0);
+  }
   float zoom = style.EffectiveZoom();
   return FloatPoint(ValueForLength(x_length, zoom, viewport_size.Width()),
                     ValueForLength(y_length, zoom, viewport_size.Height()));

third_party/blink/web_tests/external/wpt/svg/shapes/reftests/disabled-shapes-01.svg

@@ -9,15 +9,25 @@
   <g stroke="red" stroke-width="100">
     <g transform="translate(50, 50)">
       <rect/>
+      <rect width="10"/>
+      <rect height="10"/>
+      <rect width="10%"/>
+      <rect height="10%"/>
       <rect width="0" height="10"/>
       <rect width="-10" height="10"/>
       <rect height="0" width="10"/>
       <rect height="-10" width="10"/>
       <rect style="width: 0"/>
+      <rect style="width: 10px"/>
+      <rect style="width: 10%"/>
+      <rect style="width: calc(10%+10px)"/>
       <rect style="width: 0" height="10"/>
       <rect style="width: -10px"/>
       <rect style="width: -10px" height="10"/>
       <rect style="height: 0"/>
+      <rect style="height: 10px"/>
+      <rect style="height: 10%"/>
+      <rect style="height: calc(10%+10px)"/>
       <rect style="height: 0" width="10"/>
       <rect style="height: -10px"/>
       <rect style="height: -10px" width="10"/>