Changing slider values do not work properly when percent change of a step is less than one.

Source/modules/accessibility/AXNodeObject.cpp

 /*
 * Copyright (C) 2012, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 110 matching lines @@
             builder.append(' ');
     }
     return builder.toString();
 }
 
 void AXNodeObject::alterSliderValue(bool increase)
 {
     if (roleValue() != SliderRole)
         return;
 
-    if (!getAttribute(stepAttr).isEmpty())
-        changeValueByStep(increase);
-    else
-        changeValueByPercent(increase ? 5 : -5);
+    float value = valueForRange();
+    float step = stepValueForRange();

[dmazzoni, 2015/04/10 17:14:28]

It looks like stepValueForRange is implemented naively, it just returns the step
attribute.

I think better would be to get it from HTMLInputElement so that it follows the
spec correctly.

At first glance it looks like you should get it from
toHTMLInputElement(node())->createStepRange(RejectAny).step() (with appropriate
error checking, of course).

Yet another way to do it would be to try to set the value by the percentage, and
if it doesn't change, call HTMLInputElement::stepUp or stepDown.

+
+    if (getAttribute(stepAttr).isEmpty()) {
+        const float percentChange = 5;
+        float range = maxValueForRange() - minValueForRange();
+        step = range * (percentChange / 100);
+        if (step < 1)
+            step = 1;
+    }
+
+    value += increase ? step : -step;
+    setValue(String::number(value));
+    axObjectCache()->postNotification(node(), AXObjectCacheImpl::AXValueChanged);
 }
 
 String AXNodeObject::ariaAccessibilityDescription() const
 {
     String ariaLabeledBy = ariaLabeledByAttribute();
     if (!ariaLabeledBy.isEmpty())
         return ariaLabeledBy;
 
     const AtomicString& ariaLabel = getAttribute(aria_labelAttr);
     if (!ariaLabel.isEmpty())
         return ariaLabel;
 
     return String();
 }
 
 
 void AXNodeObject::ariaLabeledByElements(WillBeHeapVector<RawPtrWillBeMember<Element>>& elements) const
 {
     elementsFromAttribute(elements, aria_labeledbyAttr);
     if (!elements.size())
         elementsFromAttribute(elements, aria_labelledbyAttr);
 }
 
-void AXNodeObject::changeValueByStep(bool increase)
-{
-    float step = stepValueForRange();
-    float value = valueForRange();
-
-    value += increase ? step : -step;
-
-    setValue(String::number(value));
-
-    axObjectCache()->postNotification(node(), AXObjectCacheImpl::AXValueChanged);
-}
-
 bool AXNodeObject::computeAccessibilityIsIgnored() const
 {
 #if ENABLE(ASSERT)
     // Double-check that an AXObject is never accessed before
     // it's been initialized.
     ASSERT(m_initialized);
 #endif
 
     // If this element is within a parent that cannot have children, it should not be exposed.
     if (isDescendantOfBarrenParent())
@@ skipping 1890 matching lines @@
         WillBeHeapVector<RawPtrWillBeMember<Element>> elements;
         ariaLabeledByElements(elements);
 
         for (const auto& element : elements) {
             RefPtr<AXObject> axElement = axObjectCache()->getOrCreate(element);
             textOrder.append(AccessibilityText(ariaLabeledBy, AlternativeText, axElement));
         }
     }
 }
 
-void AXNodeObject::changeValueByPercent(float percentChange)
-{
-    float range = maxValueForRange() - minValueForRange();
-    float value = valueForRange();
-
-    value += range * (percentChange / 100);
-    setValue(String::number(value));
-
-    axObjectCache()->postNotification(node(), AXObjectCacheImpl::AXValueChanged);
-}
-
 } // namespace blink