Initial error handling code

include/core/SkFlattenableBuffers.h

Index: include/core/SkFlattenableBuffers.h
diff --git a/include/core/SkFlattenableBuffers.h b/include/core/SkFlattenableBuffers.h
index 03c03f3877e6f8e3f508d29e371d5c7ebd91624e..53d1c13023a2fa55001b50ad735cb6ad1a9ad9d8 100644
--- a/include/core/SkFlattenableBuffers.h
+++ b/include/core/SkFlattenableBuffers.h
@@ -41,14 +41,20 @@ public:
         kCrossProcess_Flag      = 1 << 0,
         kScalarIsFloat_Flag     = 1 << 1,
         kPtrIs64Bit_Flag        = 1 << 2,
+        /** The kValidation_Flag is used to force stream validations (by making
+         * sure that no operation reads past the end of the stream, for example)
+         * and error handling if any reading operation yields an invalid value.
+         */
+        kValidation_Flag        = 1 << 3,
     };
 
     void setFlags(uint32_t flags) { fFlags = flags; }
     uint32_t getFlags() const { return fFlags; }
 
-    bool isCrossProcess() const { return SkToBool(fFlags & kCrossProcess_Flag); }
+    bool isCrossProcess() const { return SkToBool(fFlags & (kCrossProcess_Flag | kValidation_Flag)); }
     bool isScalarFloat() const { return SkToBool(fFlags & kScalarIsFloat_Flag); }
     bool isPtr64Bit() const { return SkToBool(fFlags & kPtrIs64Bit_Flag); }
+    bool isValidating() const { return SkToBool(fFlags & kValidation_Flag); }
 
     // primitives
     virtual bool readBool() = 0;
@@ -64,7 +70,16 @@ public:
     virtual void* readEncodedString(size_t* length, SkPaint::TextEncoding encoding) = 0;
 
     // common data structures
-    virtual SkFlattenable* readFlattenable() = 0;
+    virtual SkFlattenable* readFlattenable(
+    /**
+      @param type   This parameter is only used when using SkValidatingReadBuffer. It will verify
+                    that the object about to be deserialized is of the given type or early return
+                    NULL otherwise. The type provided here is either the same type or the type of
+                    one of the base classes of the object to deserialize. This can effectively be
+                    bypassed by providing the type SkFlattenable::GetTypeName() here, since
+                    SkFlattenable is a base class to all other classes that can be deserialized.
+      */
+        const char* name = SkFlattenable::GetTypeName()) = 0;
     virtual void readPoint(SkPoint* point) = 0;
     virtual void readMatrix(SkMatrix* matrix) = 0;
     virtual void readIRect(SkIRect* rect) = 0;
@@ -99,9 +114,11 @@ public:
     }
 
     template <typename T> T* readFlattenableT() {
-        return static_cast<T*>(this->readFlattenable());
+        return static_cast<T*>(this->readFlattenable(T::GetTypeName()));
     }
 
+    virtual void validate(bool isValid) SK_OVERRIDE {}
+
 private:
     uint32_t fFlags;
 };
@@ -154,13 +171,22 @@ public:
 
     enum Flags {
         kCrossProcess_Flag               = 0x01,
+        /** The kValidation_Flag is used here to make sure the write operation
+         *  is symmetric with the read operation using the equivalent flag
+         *  SkFlattenableReadBuffer::kValidation_Flag.
+         */
+        kValidation_Flag                 = 0x02,
     };
 
     uint32_t getFlags() const { return fFlags; }
     void setFlags(uint32_t flags) { fFlags = flags; }
 
     bool isCrossProcess() const {
-        return SkToBool(fFlags & kCrossProcess_Flag);
+        return SkToBool(fFlags & (kCrossProcess_Flag | kValidation_Flag));
+    }
+
+    bool isValidating() const {
+        return SkToBool(fFlags & kValidation_Flag);
     }
 
     bool persistTypeface() const { return (fFlags & kCrossProcess_Flag) != 0; }