Build fix: not all types support precisions.

Currently Angle translator made the wrong assumption that all variables have a precision, and ASSERT that.

BUG=276031
TBR=alokp@chromium.org

Review URL: https://codereview.appspot.com/13113044
diff --git a/src/compiler/ShaderLang.cpp b/src/compiler/ShaderLang.cpp
index bef54fc..b1364fd 100644
--- a/src/compiler/ShaderLang.cpp
+++ b/src/compiler/ShaderLang.cpp
@@ -293,7 +293,9 @@
         *precision = SH_PRECISION_HIGHP;
         break;
     default:
-        ASSERT(false);
+        // Some types does not support precision, for example, boolean.
+        *precision = SH_PRECISION_UNDEFINED;
+        break;
     }
 
     // This size must match that queried by