[css-grid] Use transferred size over content size for automatic minimum

CSS WG has agreed to modify the spec so now the transferred size is used
(if it exists) independently if it's bigger or smaller
than the content size.
See: w3c/csswg-drafts#1149

The spec text (https://drafts.csswg.org/css-grid/#min-size-auto):
  "The automatic minimum size for a grid item in a given dimension is
   its specified size if it exists, otherwise its transferred size
   if that exists, else its content size"

This patch modifies GridTrackSizingAlgorithmStrategy::MinSizeForChild()
so it always returns the transferred size (if any).
This also updates the tests to check the new behavior.

BUG=763265

Change-Id: If6134e7d031a3f9693b8d9ca62f8f41d3146add2
Reviewed-on: https://chromium-review.googlesource.com/657098
Reviewed-by: Javier Fernandez <jfernandez@igalia.com>
Commit-Queue: Manuel Rego Casasnovas <rego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#500799}

css/css-grid-1/grid-items/grid-minimum-size-grid-items-006.html

@@ -5,7 +5,7 @@
 <link rel="help" href="http://www.w3.org/TR/css-grid-1/#min-size-auto" title="6.6. Implied Minimum Size of Grid Items">
 <link rel="match" href="ref-filled-green-100px-square-image.html">
 <meta name="flags" content="image">
-<meta name="assert" content="Checks that minimum size for grid items is the specified size for width (regardless the content size) and the transferred size for height (as it's smaller than the content size of the image).">
+<meta name="assert" content="Checks that minimum size for grid items is the specified size for width (regardless the content size) and the transferred size of the image for height (even when content size is bigger).">
 <style>
   #reference-overlapped-red {
     position: absolute;

css/css-grid-1/grid-items/grid-minimum-size-grid-items-007.html

@@ -5,7 +5,7 @@
 <link rel="help" href="http://www.w3.org/TR/css-grid-1/#min-size-auto" title="6.6. Implied Minimum Size of Grid Items">
 <link rel="match" href="ref-filled-green-100px-square-image.html">
 <meta name="flags" content="image">
-<meta name="assert" content="Checks that minimum size for grid items is the specified size for width (regardless the content size) and the content size for height (as it's smaller than the transferred size of the image).">
+<meta name="assert" content="Checks that minimum size for grid items is the specified size for width (regardless the content size) and the transferred size of the image for height (even when content size is smaller).">
 <style>
   #reference-overlapped-red {
     position: absolute;
@@ -17,12 +17,13 @@
 
   #constrained-grid {
     display: grid;
+    grid-template-columns: auto auto;
     width: 10px;
     height: 10px;
   }
 
-  #test-grid-item-overlapping-green {
-    width: 100px;
+  .test-grid-item-overlapping-green {
+    width: 50px;
     justify-self: stretch;
     align-self: stretch;
   }
@@ -31,6 +32,7 @@
 
 <div id="reference-overlapped-red"></div>
 <div id="constrained-grid">
-  <img id="test-grid-item-overlapping-green" src="support/50x100-green.png" alt="Image download support must be enabled" />
+  <img class="test-grid-item-overlapping-green" src="support/25x50-green.png" alt="Image download support must be enabled" />
+  <img class="test-grid-item-overlapping-green" src="support/25x50-green.png" alt="Image download support must be enabled" />
 </div>
 

css/css-grid-1/grid-items/grid-minimum-size-grid-items-008.html

@@ -5,7 +5,7 @@
 <link rel="help" href="http://www.w3.org/TR/css-grid-1/#min-size-auto" title="6.6. Implied Minimum Size of Grid Items">
 <link rel="match" href="ref-filled-green-100px-square-image.html">
 <meta name="flags" content="image">
-<meta name="assert" content="Checks that minimum size for grid items is the specified size for height (regardless the content size) and the transferred size for width (as it's smaller than the content size of the image).">
+<meta name="assert" content="Checks that minimum size for grid items is the specified size for height (regardless the content size) and the transferred size of the image for width (even when content size is bigger).">
 <style>
   #reference-overlapped-red {
     position: absolute;

css/css-grid-1/grid-items/grid-minimum-size-grid-items-009.html

@@ -5,7 +5,7 @@
 <link rel="help" href="http://www.w3.org/TR/css-grid-1/#min-size-auto" title="6.6. Implied Minimum Size of Grid Items">
 <link rel="match" href="ref-filled-green-100px-square-image.html">
 <meta name="flags" content="image">
-<meta name="assert" content="Checks that minimum size for grid items is the specified size for height (regardless the content size) and the content size for width (as it's smaller than the transferred size of the image).">
+<meta name="assert" content="Checks that minimum size for grid items is the specified size for height (regardless the content size) and the transferred size for width of the image (even when content size is smaller).">
 <style>
   #reference-overlapped-red {
     position: absolute;
@@ -21,8 +21,8 @@
     height: 10px;
   }
 
-  #test-grid-item-overlapping-green {
-    height: 100px;
+  .test-grid-item-overlapping-green {
+    height: 50px;
     justify-self: stretch;
     align-self: stretch;
   }
@@ -31,6 +31,7 @@
 
 <div id="reference-overlapped-red"></div>
 <div id="constrained-grid">
-  <img id="test-grid-item-overlapping-green" src="support/100x50-green.png" alt="Image download support must be enabled" />
+  <img class="test-grid-item-overlapping-green" src="support/50x25-green.png" alt="Image download support must be enabled" />
+  <img class="test-grid-item-overlapping-green" src="support/50x25-green.png" alt="Image download support must be enabled" />
 </div>
 

css/css-grid-1/grid-items/grid-minimum-size-grid-items-021.html

@@ -67,17 +67,17 @@
 
   function runTests() {
     checkGridSizeTracksAndImageSize("grid-1", "img-1", "200px", "200px", "200px", "200px", "200px", "200px");
-    checkGridSizeTracksAndImageSize("grid-2", "img-2", "10px", "10px", "200px", "50px", "200px", "200px");
+    checkGridSizeTracksAndImageSize("grid-2", "img-2", "10px", "10px", "200px", "200px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-3", "img-3", "200px", "50px", "200px", "50px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-4", "img-4", "200px", "10px", "200px", "50px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-5", "img-5", "200px", "50px", "50px", "50px", "50px", "50px");
     checkGridSizeTracksAndImageSize("grid-6", "img-6", "200px", "10px", "50px", "50px", "50px", "50px");
     checkGridSizeTracksAndImageSize("grid-7", "img-7", "200px", "225px", "200px", "200px 25px", "200px", "200px");
-    checkGridSizeTracksAndImageSize("grid-8", "img-8", "10px", "10px", "200px", "50px 25px", "200px", "200px");
+    checkGridSizeTracksAndImageSize("grid-8", "img-8", "10px", "10px", "200px", "200px 25px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-9", "img-9", "200px", "125px", "200px", "100px 25px", "200px", "200px");
-    checkGridSizeTracksAndImageSize("grid-10", "img-10", "200px", "10px", "200px", "50px 25px", "200px", "200px");
+    checkGridSizeTracksAndImageSize("grid-10", "img-10", "200px", "10px", "200px", "100px 25px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-11", "img-11", "200px", "125px", "100px", "100px 25px", "100px", "100px");
-    checkGridSizeTracksAndImageSize("grid-12", "img-12", "200px", "10px", "100px", "50px 25px", "100px", "100px");
+    checkGridSizeTracksAndImageSize("grid-12", "img-12", "200px", "10px", "100px", "100px 25px", "100px", "100px");
     checkGridSizeTracksAndImageSize("grid-13", "img-13", "200px", "200px", "200px", "200px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-14", "img-14", "10px", "10px", "200px", "200px", "200px", "200px");
     checkGridSizeTracksAndImageSize("grid-15", "img-15", "200px", "200px", "200px", "200px", "200px", "200px");