Remove predefined precision qualifiers from ESSL3 samplers

New sampler types in ESSL3 should not have default precision qualifiers.
This is specified in ESSL 3.00.4 section 4.5.4.

BUG=angleproject:1222
TEST=angle_unittests

Change-Id: I9c8e7a5fbb4278db80de79bcaeebaf23e64242a0
Reviewed-on: https://chromium-review.googlesource.com/312048
Tryjob-Request: Olli Etuaho <oetuaho@nvidia.com>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
diff --git a/src/compiler/translator/Compiler.h b/src/compiler/translator/Compiler.h
index 736d9ef..c00a8f9 100644
--- a/src/compiler/translator/Compiler.h
+++ b/src/compiler/translator/Compiler.h
@@ -179,6 +179,8 @@
     bool tagUsedFunctions();
     void internalTagUsedFunction(size_t index);
 
+    void initSamplerDefaultPrecision(TBasicType samplerType);
+
     // Removes unused function declarations and prototypes from the AST
     class UnusedPredicate;
     bool pruneUnusedFunctions(TIntermNode *root);