enforce 16byte alignment in shader contexts

src/core/SkShader.cpp

Index: src/core/SkShader.cpp
diff --git a/src/core/SkShader.cpp b/src/core/SkShader.cpp
index e36df5b5af057df6fcacdff6277e3e7f8d667c46..fd5fb00b886fe9ca09ae53aab42cbe0c3329266d 100644
--- a/src/core/SkShader.cpp
+++ b/src/core/SkShader.cpp
@@ -86,6 +86,10 @@ bool SkShader::asLuminanceColor(SkColor* colorPtr) const {
 }
 
 SkShader::Context* SkShader::createContext(const ContextRec& rec, void* storage) const {
+    // Currently we require each context to be allocated on 16byte boundary as some of our
+    // subclasses need that. Hence we check the ptr here.
+    SkASSERT(SkIsAlign16((intptr_t)storage));
+
     if (!this->computeTotalInverse(rec, nullptr)) {
         return nullptr;
     }
@@ -96,7 +100,17 @@ SkShader::Context* SkShader::onCreateContext(const ContextRec& rec, void*) const
     return nullptr;
 }
 
-size_t SkShader::contextSize(const ContextRec&) const {
+size_t SkShader::contextSize(const ContextRec& rec) const {
+    size_t size = this->onContextSize(rec);
+
+    // Currently we require each context to be allocated on 16byte boundary as some of our
+    // subclasses need that. Hence we check the size here.
+    SkASSERT(SkIsAlign16(size));
+
+    return size;
+}
+
+size_t SkShader::onContextSize(const ContextRec&) const {
     return 0;
 }