Initial error handling code

src/core/SkXfermode.cpp

Index: src/core/SkXfermode.cpp
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index e50e4f5ce58179cacbea609785d69a27bea8cb4f..7c8c1259a3fa0aa0108b846dc95a80d4b73892d7 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -12,6 +12,7 @@
 #include "SkFlattenableBuffers.h"
 #include "SkMathPriv.h"
 #include "SkString.h"
+#include "SkValidationUtils.h"
 
 SK_DEFINE_INST_COUNT(SkXfermode)
 
@@ -1409,13 +1410,20 @@ public:
 protected:
     SkProcCoeffXfermode(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {
         fMode = (SkXfermode::Mode)buffer.read32();
-
-        const ProcCoeff& rec = gProcCoeffs[fMode];
-        // these may be valid, or may be CANNOT_USE_COEFF
-        fSrcCoeff = rec.fSC;
-        fDstCoeff = rec.fDC;
-        // now update our function-ptr in the super class
-        this->INHERITED::setProc(rec.fProc);
+        bool modeIsValid = SkIsValidMode(fMode);
+        if (modeIsValid) {
+            const ProcCoeff& rec = gProcCoeffs[fMode];
+            // these may be valid, or may be CANNOT_USE_COEFF
+            fSrcCoeff = rec.fSC;
+            fDstCoeff = rec.fDC;
+            // now update our function-ptr in the super class
+            this->INHERITED::setProc(rec.fProc);
+        } else {
+            fSrcCoeff = fDstCoeff = CANNOT_USE_COEFF;
+        }
+        buffer.validate(modeIsValid &&
+                        (SkIsValidCoeff(fSrcCoeff) || (fSrcCoeff == CANNOT_USE_COEFF)) &&
+                        (SkIsValidCoeff(fDstCoeff) || (fDstCoeff == CANNOT_USE_COEFF)));
     }
 
     virtual void flatten(SkFlattenableWriteBuffer& buffer) const SK_OVERRIDE {
@@ -1688,6 +1696,44 @@ void SkDstOutXfermode::toString(SkString* str) const {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+SkFlattenable::Factory SkProcXfermode::GetFactory(SkFlattenable::Type type) {
+    switch(type) {
+    case SkFlattenable::kSkClearXfermode_Type:
+        return SkClearXfermode::CreateProc;
+    case SkFlattenable::kSkDstInXfermode_Type:
+        return SkDstInXfermode::CreateProc;
+    case SkFlattenable::kSkDstOutXfermode_Type:
+        return SkDstOutXfermode::CreateProc;
+    case SkFlattenable::kSkProcCoeffXfermode_Type:
+        return SkProcCoeffXfermode::CreateProc;
+    case SkFlattenable::kSkSrcXfermode_Type:
+        return SkSrcXfermode::CreateProc;
+    default:
+        break;
+    }
+    return NULL;
+}
+
+SkFlattenable::TypeCheck SkProcXfermode::GetTypeCheck(SkFlattenable::Type type) {
+    switch(type) {
+    case SkFlattenable::kSkClearXfermode_Type:
+        return SkClearXfermode::IsA;
+    case SkFlattenable::kSkDstInXfermode_Type:
+        return SkDstInXfermode::IsA;
+    case SkFlattenable::kSkDstOutXfermode_Type:
+        return SkDstOutXfermode::IsA;
+    case SkFlattenable::kSkProcCoeffXfermode_Type:
+        return SkProcCoeffXfermode::IsA;
+    case SkFlattenable::kSkSrcXfermode_Type:
+        return SkSrcXfermode::IsA;
+    default:
+        break;
+    }
+    return NULL;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 SkXfermode* SkXfermode::Create(Mode mode) {
     SkASSERT(SK_ARRAY_COUNT(gProcCoeffs) == kModeCount);
     SkASSERT((unsigned)mode < kModeCount);