Improve comparison of intervals in SVGSMILElement::resolveFirstInterval

For open-ended intervals such as [3) - i.e. begin=3s and end/duration/etc
unspecified - every call to resolveFirstInterval() would think that a new
interval had been created, and notify/require a reschedule of the
animations.
Add a new type SMILInterval and a suitable operator for that, and then
use it to compare the raw values (i.e. if both endpoints are exacly the same.)

BUG=377329

Review URL: https://codereview.chromium.org/298043005

git-svn-id: svn://svn.chromium.org/blink/trunk@175122 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/svg/animation/SMILTime.h

@@ -80,6 +80,14 @@ private:
     Origin m_origin;
 };
 
+struct SMILInterval {
+    SMILInterval() { }
+    SMILInterval(const SMILTime& begin, const SMILTime& end) : begin(begin), end(end) { }
+
+    SMILTime begin;
+    SMILTime end;
+};
+
 inline bool operator==(const SMILTime& a, const SMILTime& b) { return a.isFinite() && a.value() == b.value(); }
 inline bool operator!(const SMILTime& a) { return !a.isFinite() || !a.value(); }
 inline bool operator!=(const SMILTime& a, const SMILTime& b) { return !operator==(a, b); }
@@ -94,6 +102,13 @@ SMILTime operator-(const SMILTime&, const SMILTime&);
 // So multiplying times does not make too much sense but SMIL defines it for duration * repeatCount
 SMILTime operator*(const SMILTime&, const SMILTime&);
 
+inline bool operator!=(const SMILInterval& a, const SMILInterval& b)
+{
+    // Compare the "raw" values since the operator!= for SMILTime always return
+    // true for non-finite times.
+    return a.begin.value() != b.begin.value() || a.end.value() != b.end.value();
+}
+
 }
 
 #endif // SMILTime_h

third_party/WebKit/Source/core/svg/animation/SVGSMILElement.cpp

@@ -935,14 +935,13 @@ void SVGSMILElement::resolveInterval(bool first, SMILTime& beginResult, SMILTime
 
 void SVGSMILElement::resolveFirstInterval()
 {
-    SMILTime begin;
-    SMILTime end;
-    resolveInterval(true, begin, end);
-    ASSERT(!begin.isIndefinite());
+    SMILInterval firstInterval;
+    resolveInterval(true, firstInterval.begin, firstInterval.end);
+    ASSERT(!firstInterval.begin.isIndefinite());
 
-    if (!begin.isUnresolved() && (begin != m_intervalBegin || end != m_intervalEnd)) {
-        m_intervalBegin = begin;
-        m_intervalEnd = end;
+    if (!firstInterval.begin.isUnresolved() && firstInterval != SMILInterval(m_intervalBegin, m_intervalEnd)) {
+        m_intervalBegin = firstInterval.begin;
+        m_intervalEnd = firstInterval.end;
         notifyDependentsIntervalChanged();
         m_nextProgressTime = min(m_nextProgressTime, m_intervalBegin);