Adding error checks to SkRBuffer

src/core/SkRegion.cpp

Index: src/core/SkRegion.cpp
diff --git a/src/core/SkRegion.cpp b/src/core/SkRegion.cpp
index 0d9198f9f7fbd48d9c191b5118bb81db10c2cbc4..baedf2aea82c2f06a49db288bdaeaa22f243339b 100644
--- a/src/core/SkRegion.cpp
+++ b/src/core/SkRegion.cpp
@@ -1138,15 +1138,12 @@ size_t SkRegion::readFromMemory(const void* storage, size_t length) {
     SkRegion                tmp;
     int32_t                 count;
 
-    count = buffer.readS32();
-    if (count >= 0) {
-        buffer.read(&tmp.fBounds, sizeof(tmp.fBounds));
+    if (buffer.readS32(&count) && (count >= 0) && buffer.read(&tmp.fBounds, sizeof(tmp.fBounds))) {
         if (count == 0) {
             tmp.fRunHead = SkRegion_gRectRunHeadPtr;
         } else {
-            int32_t ySpanCount = buffer.readS32();
-            int32_t intervalCount = buffer.readS32();
-            if (buffer.isValid()) {
+            int32_t ySpanCount, intervalCount;
+            if (buffer.readS32(&ySpanCount) && buffer.readS32(&intervalCount)) {
                 tmp.allocateRuns(count, ySpanCount, intervalCount);
                 buffer.read(tmp.fRunHead->writable_runs(), count * sizeof(RunType));
             }