Implement toString() funtion in DOMMatrixReadOnly.

add toString() funtion in DOMMatrixReadOnly.
refer to detail spec([1])

[1] = https://drafts.fxtf.org/geometry/#dom-dommatrixreadonly-stringifier

BUG=388780

Review-Url: https://codereview.chromium.org/2273663002
Cr-Commit-Position: refs/heads/master@{#414228}

third_party/WebKit/LayoutTests/fast/dom/geometry-interfaces-dom-matrix-readonly.html

@@ -39,6 +39,18 @@ test(function() {
     assert_equals(matrix3d.m44, 16.6);
 }, "DOMMatrixReadOnly constructor - 3D matrix");
 
+test(function() {
+    var matrix2d = new DOMMatrixReadOnly([1, 2, 3, 3.1, 2, 1]);
+    assert_true(matrix2d.is2D);
+    assert_equals(matrix2d.toString(), "matrix(1, 2, 3, 3.1, 2, 1)");
+}, "DOMMatrixReadOnly toString() - 2D matrix");
+
+test(function() {
+    var matrix3d = new DOMMatrixReadOnly([1, 2, 3, 4, 5, 6, 7, 8, 9, 10.1, 11, 12, 13, 14, 15, 16.6]);
+    assert_false(matrix3d.is2D);
+    assert_equals(matrix3d.toString(), "matrix3d(1, 2, 3, 4, 5, 6, 7, 8, 9, 10.1, 11, 12, 13, 14, 15, 16.6)");
+}, "DOMMatrixReadOnly toString() - 3D matrix");
+
 test(function() {
     assert_throws(new TypeError(), function() { new DOMMatrixReadOnly(1, 2, 3, 4, 5, 6); },
             "DOMMatrixReadOnly constructor only accepts 1 argument");

third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt

@@ -1057,6 +1057,7 @@ interface DOMMatrixReadOnly
     method skewY
     method toFloat32Array
     method toFloat64Array
+    method toString
     method translate
 interface DOMParser
     attribute @@toStringTag

third_party/WebKit/Source/core/dom/DOMMatrixReadOnly.cpp

@@ -128,4 +128,23 @@ DOMFloat64Array* DOMMatrixReadOnly::toFloat64Array() const
     return DOMFloat64Array::create(array, 16);
 }
 
+const String DOMMatrixReadOnly::toString() const
+{
+    std::stringstream stream;
+    if (is2D()) {
+        stream << "matrix("
+        << a() << ", " << b() << ", " << c() << ", "
+        << d() << ", " << e() << ", " << f();
+    } else {
+        stream << "matrix3d("
+        << m11() << ", " << m12() << ", " << m13() << ", " << m14() << ", "
+        << m21() << ", " << m22() << ", " << m23() << ", " << m24() << ", "
+        << m31() << ", " << m32() << ", " << m33() << ", " << m34() << ", "
+        << m41() << ", " << m42() << ", " << m43() << ", " << m44();
+    }
+    stream << ")";
+
+    return String(stream.str().c_str());
+}
+
 } // namespace blink

third_party/WebKit/Source/core/dom/DOMMatrixReadOnly.h

@@ -63,6 +63,8 @@ public:
     DOMFloat32Array* toFloat32Array() const;
     DOMFloat64Array* toFloat64Array() const;
 
+    const String toString() const;
+
     const TransformationMatrix& matrix() const { return *m_matrix; }
 
     DEFINE_INLINE_TRACE() { }

third_party/WebKit/Source/core/dom/DOMMatrixReadOnly.idl

@@ -64,4 +64,5 @@
 
     Float32Array toFloat32Array();
     Float64Array toFloat64Array();
+    stringifier;
 };