For WebGL warn on late extension directive

A previous change based on ESSL 1.00 spec had made it an error in all
cases when an extension directive appeared in a shader after the first
non-preprocessor token. However, this is incorrect for WebGL 1.0 so
adding warning case for WebGL.

BUG=chromium:971660

Change-Id: I026fe60e8b1876de65b001b676f7a0552739a20c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1648661
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Tobin Ehlis <tobine@google.com>

Author: tobine

src/compiler/preprocessor/DiagnosticsBase.cpp

@@ -115,6 +115,8 @@ const char *Diagnostics::message(ID id)
             return "invalid file number";
         case PP_INVALID_LINE_DIRECTIVE:
             return "invalid line directive";
+        case PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL1:
+            return "extension directive must occur before any non-preprocessor tokens in ESSL1";
         case PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL3:
             return "extension directive must occur before any non-preprocessor tokens in ESSL3";
         case PP_UNDEFINED_SHIFT:
@@ -129,7 +131,7 @@ const char *Diagnostics::message(ID id)
             return "unexpected token after conditional expression";
         case PP_UNRECOGNIZED_PRAGMA:
             return "unrecognized pragma";
-        case PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL1:
+        case PP_NON_PP_TOKEN_BEFORE_EXTENSION_WEBGL:
             return "extension directive should occur before any non-preprocessor tokens";
         case PP_WARNING_MACRO_NAME_RESERVED:
             return "macro name with a double underscore is reserved - unintented behavior is "

src/compiler/preprocessor/DiagnosticsBase.h

@@ -73,6 +73,7 @@ class Diagnostics
         PP_WARNING_BEGIN,
         PP_EOF_IN_DIRECTIVE,
         PP_UNRECOGNIZED_PRAGMA,
+        PP_NON_PP_TOKEN_BEFORE_EXTENSION_WEBGL,
         PP_WARNING_MACRO_NAME_RESERVED,
         PP_WARNING_END
     };

src/compiler/preprocessor/DirectiveParser.cpp

@@ -676,8 +676,16 @@ void DirectiveParser::parseExtension(Token *token)
         }
         else
         {
-            mDiagnostics->report(Diagnostics::PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL1,
-                                 token->location, token->text);
+            if (mSettings.shaderSpec == SH_WEBGL_SPEC)
+            {
+                mDiagnostics->report(Diagnostics::PP_NON_PP_TOKEN_BEFORE_EXTENSION_WEBGL,
+                                     token->location, token->text);
+            }
+            else
+            {
+                mDiagnostics->report(Diagnostics::PP_NON_PP_TOKEN_BEFORE_EXTENSION_ESSL1,
+                                     token->location, token->text);
+            }
         }
     }
     if (valid)