Rework the checks for too-few values in feColorMatrix filter.

Source/platform/graphics/filters/FEColorMatrix.cpp

Index: Source/platform/graphics/filters/FEColorMatrix.cpp
diff --git a/Source/platform/graphics/filters/FEColorMatrix.cpp b/Source/platform/graphics/filters/FEColorMatrix.cpp
index 75c66bafa9cf21c24e5577b6f9186708530c89a6..425f35c1ecb6bd4d41ead49f86582bae400a83c2 100644
--- a/Source/platform/graphics/filters/FEColorMatrix.cpp
+++ b/Source/platform/graphics/filters/FEColorMatrix.cpp
@@ -31,6 +31,8 @@
 
 namespace blink {
 
+static const unsigned kColorMatrixSize = 20;
+
 FEColorMatrix::FEColorMatrix(Filter* filter, ColorMatrixType type, const Vector<float>& values)
     : FilterEffect(filter)
     , m_type(type)
@@ -69,7 +71,7 @@ bool FEColorMatrix::setValues(const Vector<float> &values)
     return true;
 }
 
-static void saturateMatrix(float s, SkScalar matrix[20])
+static void saturateMatrix(float s, SkScalar matrix[kColorMatrixSize])
 {
     matrix[0] = 0.213f + 0.787f * s;
     matrix[1] = 0.715f - 0.715f * s;
@@ -88,7 +90,7 @@ static void saturateMatrix(float s, SkScalar matrix[20])
     matrix[19] = 0;
 }
 
-static void hueRotateMatrix(float hue, SkScalar matrix[20])
+static void hueRotateMatrix(float hue, SkScalar matrix[kColorMatrixSize])
 {
     float cosHue = cosf(hue * piFloat / 180);
     float sinHue = sinf(hue * piFloat / 180);
@@ -109,34 +111,41 @@ static void hueRotateMatrix(float hue, SkScalar matrix[20])
     matrix[19] = 0;
 }
 
-static void luminanceToAlphaMatrix(SkScalar matrix[20])
+static void luminanceToAlphaMatrix(SkScalar matrix[kColorMatrixSize])
 {
-    memset(matrix, 0, 20 * sizeof(SkScalar));
+    memset(matrix, 0, kColorMatrixSize * sizeof(SkScalar));
     matrix[15] = 0.2125f;
     matrix[16] = 0.7154f;
     matrix[17] = 0.0721f;
 }
 
-static SkColorFilter* createColorFilter(ColorMatrixType type, const float* values)
+static SkColorFilter* createColorFilter(ColorMatrixType type, const Vector<float>& values)
 {
-    SkScalar matrix[20];
+    // Use defaults if values contains too few values. See SVGFEColorMatrixElement::build
+    SkScalar matrix[kColorMatrixSize];
+    memset(matrix, 0, kColorMatrixSize * sizeof(SkScalar));
+    matrix[0] = matrix[6] = matrix[12] = matrix[18] = 1;
+
     switch (type) {
     case FECOLORMATRIX_TYPE_UNKNOWN:
         break;
     case FECOLORMATRIX_TYPE_MATRIX:
-        for (int i = 0; i < 20; ++i)
-            matrix[i] = values[i];
-
+        if (values.size() >= kColorMatrixSize) {
+            for (unsigned i = 0; i < kColorMatrixSize; ++i)
+                matrix[i] = values[i];
+        }
         matrix[4] *= SkScalar(255);
         matrix[9] *= SkScalar(255);
         matrix[14] *= SkScalar(255);
         matrix[19] *= SkScalar(255);
         break;
     case FECOLORMATRIX_TYPE_SATURATE:
-        saturateMatrix(values[0], matrix);
+        if (values.size())
+            saturateMatrix(values[0], matrix);
         break;
     case FECOLORMATRIX_TYPE_HUEROTATE:
-        hueRotateMatrix(values[0], matrix);
+        if (values.size())
+            hueRotateMatrix(values[0], matrix);
         break;
     case FECOLORMATRIX_TYPE_LUMINANCETOALPHA:
         luminanceToAlphaMatrix(matrix);
@@ -149,13 +158,13 @@ bool FEColorMatrix::affectsTransparentPixels()
 {
     // Because the input pixels are premultiplied, the only way clear pixels can be
     // painted is if the additive component for the alpha is not 0.
-    return m_type == FECOLORMATRIX_TYPE_MATRIX && m_values[19] > 0;
+    return m_type == FECOLORMATRIX_TYPE_MATRIX && m_values.size() >= kColorMatrixSize && m_values[19] > 0;
 }
 
 PassRefPtr<SkImageFilter> FEColorMatrix::createImageFilter(SkiaImageFilterBuilder* builder)
 {
     RefPtr<SkImageFilter> input(builder->build(inputEffect(0), operatingColorSpace()));
-    SkAutoTUnref<SkColorFilter> filter(createColorFilter(m_type, m_values.data()));
+    SkAutoTUnref<SkColorFilter> filter(createColorFilter(m_type, m_values));
     SkImageFilter::CropRect rect = getCropRect(builder->cropOffset());
     return adoptRef(SkColorFilterImageFilter::Create(filter, input.get(), &rect));
 }