fixed skslc SPIR-V memory error

BUG=skia:6446

Change-Id: Ibc55124db60d6a05964ddcd02d285e313379f93e
Reviewed-on: https://skia-review.googlesource.com/10756
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/sksl/SkSLSPIRVCodeGenerator.h b/src/sksl/SkSLSPIRVCodeGenerator.h
index 1cdc653..ea160b1 100644
--- a/src/sksl/SkSLSPIRVCodeGenerator.h
+++ b/src/sksl/SkSLSPIRVCodeGenerator.h
@@ -74,7 +74,8 @@
     , fBoolTrue(0)
     , fBoolFalse(0)
     , fSetupFragPosition(false)
-    , fCurrentBlock(0) {
+    , fCurrentBlock(0)
+    , fSynthetics(nullptr, errors) {
         this->setupIntrinsics();
     }
 
@@ -299,6 +300,8 @@
     std::stack<SpvId> fContinueTarget;
     SpvId fRTHeightStructId = (SpvId) -1;
     SpvId fRTHeightFieldIndex = (SpvId) -1;
+    // holds variables synthesized during output, for lifetime purposes
+    SymbolTable fSynthetics;
 
     friend class PointerLValue;
     friend class SwizzleLValue;