Add GM to test out blurmaskfilter occluders

src/effects/SkBlurMaskFilter.cpp

Index: src/effects/SkBlurMaskFilter.cpp
diff --git a/src/effects/SkBlurMaskFilter.cpp b/src/effects/SkBlurMaskFilter.cpp
index 9e0315f2b7471829037429ff537562bbda92a19e..2d03077a34b1252368c13a549db860b21d8e0e83 100644
--- a/src/effects/SkBlurMaskFilter.cpp
+++ b/src/effects/SkBlurMaskFilter.cpp
@@ -38,7 +38,7 @@ SkScalar SkBlurMaskFilter::ConvertRadiusToSigma(SkScalar radius) {
 
 class SkBlurMaskFilterImpl : public SkMaskFilter {
 public:
-    SkBlurMaskFilterImpl(SkScalar sigma, SkBlurStyle, uint32_t flags);
+    SkBlurMaskFilterImpl(SkScalar sigma, SkBlurStyle, const SkRect& occluder, uint32_t flags);
 
     // overrides from SkMaskFilter
     SkMask::Format getFormat() const override;
@@ -96,8 +96,12 @@ private:
     // a request like 10,000)
     static const SkScalar kMAX_BLUR_SIGMA;
 
+    // This flag should never escape from serialization
+    static const int kInternalFlag_HasOccluder = 0x08;
+
     SkScalar    fSigma;
     SkBlurStyle fBlurStyle;
+    SkRect      fOccluder;
     uint32_t    fBlurFlags;
 
     SkBlurQuality getQuality() const {
@@ -122,27 +126,31 @@ private:
 
 const SkScalar SkBlurMaskFilterImpl::kMAX_BLUR_SIGMA = SkIntToScalar(128);
 
-sk_sp<SkMaskFilter> SkBlurMaskFilter::Make(SkBlurStyle style, SkScalar sigma, uint32_t flags) {
+sk_sp<SkMaskFilter> SkBlurMaskFilter::Make(SkBlurStyle style, SkScalar sigma, 
+                                           const SkRect& occluder, uint32_t flags) {
     if (!SkScalarIsFinite(sigma) || sigma <= 0) {
         return nullptr;
     }
     if ((unsigned)style > (unsigned)kLastEnum_SkBlurStyle) {
         return nullptr;
     }
-    if (flags > SkBlurMaskFilter::kAll_BlurFlag) {
-        return nullptr;
-    }
-    return sk_sp<SkMaskFilter>(new SkBlurMaskFilterImpl(sigma, style, flags));
+    SkASSERT(flags <= SkBlurMaskFilter::kAll_BlurFlag);
+    flags &= SkBlurMaskFilter::kAll_BlurFlag;
+
+    return sk_sp<SkMaskFilter>(new SkBlurMaskFilterImpl(sigma, style, occluder, flags));
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
-SkBlurMaskFilterImpl::SkBlurMaskFilterImpl(SkScalar sigma, SkBlurStyle style, uint32_t flags)
+SkBlurMaskFilterImpl::SkBlurMaskFilterImpl(SkScalar sigma, SkBlurStyle style,
+                                           const SkRect& occluder, uint32_t flags)
     : fSigma(sigma)
     , fBlurStyle(style)
+    , fOccluder(occluder)
     , fBlurFlags(flags) {
     SkASSERT(fSigma > 0);
     SkASSERT((unsigned)style <= kLastEnum_SkBlurStyle);
+    fOccluder.sort();
     SkASSERT(flags <= SkBlurMaskFilter::kAll_BlurFlag);
 }
 
@@ -584,8 +592,17 @@ sk_sp<SkFlattenable> SkBlurMaskFilterImpl::CreateProc(SkReadBuffer& buffer) {
     const SkScalar sigma = buffer.readScalar();
     const unsigned style = buffer.readUInt();
     const unsigned flags = buffer.readUInt();
+
+    SkRect occluder;
+    if (flags & kInternalFlag_HasOccluder) {
+        buffer.readRect(&occluder);
+    } else {
+        occluder.setEmpty();
+    }
+
     if (style <= kLastEnum_SkBlurStyle) {
-        return SkBlurMaskFilter::Make((SkBlurStyle)style, sigma, flags);
+        return SkBlurMaskFilter::Make((SkBlurStyle)style, sigma, occluder,
+                                      flags & ~kInternalFlag_HasOccluder);
     }
     return nullptr;
 }
@@ -593,7 +610,11 @@ sk_sp<SkFlattenable> SkBlurMaskFilterImpl::CreateProc(SkReadBuffer& buffer) {
 void SkBlurMaskFilterImpl::flatten(SkWriteBuffer& buffer) const {
     buffer.writeScalar(fSigma);
     buffer.writeUInt(fBlurStyle);
-    buffer.writeUInt(fBlurFlags);
+
+    SkASSERT(!(fBlurFlags & kInternalFlag_HasOccluder));
+    buffer.writeUInt(fBlurFlags | kInternalFlag_HasOccluder);
+
+    buffer.writeRect(fOccluder);
 }
 
 #if SK_SUPPORT_GPU