ParallelCompile: Parallelize shader translation

This changes to construct a new ShHandle of compiler for each Shader,
and use it to translate the shader source in a background thread.

Bug: chromium:849576

Change-Id: Ib49952c7292321ee6aa1c5996f8f7927f40d8f04
Reviewed-on: https://chromium-review.googlesource.com/1177195
Commit-Queue: Jie A Chen <jie.a.chen@intel.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/null/ShaderNULL.cpp b/src/libANGLE/renderer/null/ShaderNULL.cpp
index 4e3b9e7..f6edc87 100644
--- a/src/libANGLE/renderer/null/ShaderNULL.cpp
+++ b/src/libANGLE/renderer/null/ShaderNULL.cpp
@@ -30,7 +30,7 @@
     return 0;
 }
 
-bool ShaderNULL::postTranslateCompile(gl::Compiler *compiler, std::string *infoLog)
+bool ShaderNULL::postTranslateCompile(gl::ShCompilerInstance *compiler, std::string *infoLog)
 {
     return true;
 }