(reland) Do not let text-size-adjust override accessibility font settings

The text autosizer is used for both making desktop pages more legible
on mobile, and for applying the accessibility font scale factor. When
text-size-adjust support was added, pages were able to override the
accessibility setting in addition to the autosizing multiplier.

This patch ensures accessibility font scale settings are respected even
with text-size-adjust. A followup bug has been filed (crbug.com/645717)
for moving the accessibility font scale factor out of the autosizer.

This patch also re-enables support for text-size-adjust which was
disabled temporarily due to breaking accessibility settings.

This was reverted due to a forgotten "!" in checking whether the
viewport was specified by the author in TextAutosizer.cpp. A new test
has been added to catch this in the future. The unneeded meta viewport
declarations in all other tests have been removed because they had
no effect with the meta viewport setting disabled.

Original review:
https://codereview.chromium.org/2329733002

BUG=645269,646342

Review-Url: https://codereview.chromium.org/2340553003
Cr-Commit-Position: refs/heads/master@{#418488}

third_party/WebKit/Source/core/layout/TextAutosizer.cpp

@@ -109,8 +109,8 @@ void TextAutosizer::writeClusterDebugInfo(Cluster* cluster)
     }
     String pageInfo = "";
     if (cluster->m_root->isLayoutView()) {
-        pageInfo = String::format("; pageinfo: bm %f * (lw %d / fw %d)",
-            m_pageInfo.m_baseMultiplier, m_pageInfo.m_layoutWidth, m_pageInfo.m_frameWidth);
+        pageInfo = String::format("; pageinfo: afsf %f * dsa %f * (lw %d / fw %d)",
+            m_pageInfo.m_accessibilityFontScaleFactor, m_pageInfo.m_deviceScaleAdjustment, m_pageInfo.m_layoutWidth, m_pageInfo.m_frameWidth);
     }
     float multiplier = cluster->m_flags & SUPPRESSING ? 1.0 : cluster->m_multiplier;
     writeDebugInfo(const_cast<LayoutBlock*>(cluster->m_root),
@@ -552,24 +552,27 @@ void TextAutosizer::updatePageInfo()
         IntSize layoutSize = mainFrame->view()->layoutSize();
         m_pageInfo.m_layoutWidth = horizontalWritingMode ? layoutSize.width() : layoutSize.height();
 
-        // Compute the base font scale multiplier based on device and accessibility settings.
-        m_pageInfo.m_baseMultiplier = m_document->settings()->accessibilityFontScaleFactor();
+        // TODO(pdr): Accessibility should be moved out of the text autosizer. See: crbug.com/645717.
+        m_pageInfo.m_accessibilityFontScaleFactor = m_document->settings()->accessibilityFontScaleFactor();
+
         // If the page has a meta viewport or @viewport, don't apply the device scale adjustment.
-        const ViewportDescription& viewportDescription = mainFrame->document()->viewportDescription();
-        if (!viewportDescription.isSpecifiedByAuthor()) {
-            float deviceScaleAdjustment = m_document->settings()->deviceScaleAdjustment();
-            m_pageInfo.m_baseMultiplier *= deviceScaleAdjustment;
-        }
+        if (!mainFrame->document()->viewportDescription().isSpecifiedByAuthor())
+            m_pageInfo.m_deviceScaleAdjustment = m_document->settings()->deviceScaleAdjustment();
+        else
+            m_pageInfo.m_deviceScaleAdjustment = 1.0f;
 
+        // TODO(pdr): pageNeedsAutosizing should take into account whether text-size-adjust is used
+        // anywhere on the page because that also needs to trigger autosizing. See: crbug.com/646237.
         m_pageInfo.m_pageNeedsAutosizing = !!m_pageInfo.m_frameWidth
-            && (m_pageInfo.m_baseMultiplier * (static_cast<float>(m_pageInfo.m_layoutWidth) / m_pageInfo.m_frameWidth) > 1.0f);
+            && (m_pageInfo.m_accessibilityFontScaleFactor * m_pageInfo.m_deviceScaleAdjustment * (static_cast<float>(m_pageInfo.m_layoutWidth) / m_pageInfo.m_frameWidth) > 1.0f);
     }
 
     if (m_pageInfo.m_pageNeedsAutosizing) {
         // If page info has changed, multipliers may have changed. Force a layout to recompute them.
         if (m_pageInfo.m_frameWidth != previousPageInfo.m_frameWidth
             || m_pageInfo.m_layoutWidth != previousPageInfo.m_layoutWidth
-            || m_pageInfo.m_baseMultiplier != previousPageInfo.m_baseMultiplier
+            || m_pageInfo.m_accessibilityFontScaleFactor != previousPageInfo.m_accessibilityFontScaleFactor
+            || m_pageInfo.m_deviceScaleAdjustment != previousPageInfo.m_deviceScaleAdjustment
             || m_pageInfo.m_settingEnabled != previousPageInfo.m_settingEnabled)
             setAllTextNeedsLayout();
     } else if (previousPageInfo.m_hasAutosized) {
@@ -901,9 +904,10 @@ float TextAutosizer::multiplierFromBlock(const LayoutBlock* block)
 
     // Block width, in CSS pixels.
     float blockWidth = widthFromBlock(block);
-    float multiplier = m_pageInfo.m_frameWidth ? std::min(blockWidth, static_cast<float>(m_pageInfo.m_layoutWidth)) / m_pageInfo.m_frameWidth : 1.0f;
-
-    return std::max(m_pageInfo.m_baseMultiplier * multiplier, 1.0f);
+    float layoutWidth = std::min(blockWidth, static_cast<float>(m_pageInfo.m_layoutWidth));
+    float multiplier = m_pageInfo.m_frameWidth ? layoutWidth / m_pageInfo.m_frameWidth : 1.0f;
+    multiplier *= m_pageInfo.m_accessibilityFontScaleFactor * m_pageInfo.m_deviceScaleAdjustment;
+    return std::max(multiplier, 1.0f);
 }
 
 const LayoutBlock* TextAutosizer::deepestBlockContainingAllText(Cluster* cluster)
@@ -988,10 +992,10 @@ void TextAutosizer::applyMultiplier(LayoutObject* layoutObject, float multiplier
 {
     ASSERT(layoutObject);
     ComputedStyle& currentStyle = layoutObject->mutableStyleRef();
-    // TODO(pdr): text-size-adjust is temporarily not honored due to
-    // breaking accessibility settings. See: https://645269.
-    if (false && !currentStyle.getTextSizeAdjust().isAuto()) {
-        multiplier = currentStyle.getTextSizeAdjust().multiplier();
+    if (!currentStyle.getTextSizeAdjust().isAuto()) {
+        // The accessibility font scale factor is applied by the autosizer so we need to apply that
+        // scale factor on top of the text-size-adjust multiplier.
+        multiplier = currentStyle.getTextSizeAdjust().multiplier() * m_pageInfo.m_accessibilityFontScaleFactor;
     } else if (multiplier < 1) {
         // Unlike text-size-adjust, the text autosizer should only inflate fonts.
         multiplier = 1;

third_party/WebKit/Source/core/layout/TextAutosizer.h

@@ -237,7 +237,8 @@ private:
         PageInfo()
             : m_frameWidth(0)
             , m_layoutWidth(0)
-            , m_baseMultiplier(0)
+            , m_accessibilityFontScaleFactor(1)
+            , m_deviceScaleAdjustment(1)
             , m_pageNeedsAutosizing(false)
             , m_hasAutosized(false)
             , m_settingEnabled(false)
@@ -246,7 +247,8 @@ private:
 
         int m_frameWidth; // LocalFrame width in density-independent pixels (DIPs).
         int m_layoutWidth; // Layout width in CSS pixels.
-        float m_baseMultiplier; // Includes accessibility font scale factor and device scale adjustment.
+        float m_accessibilityFontScaleFactor;
+        float m_deviceScaleAdjustment;
         bool m_pageNeedsAutosizing;
         bool m_hasAutosized;
         bool m_settingEnabled;