Fix GLSL compilation with non-ascii characters

WebGL call to glShaderSource failing when a comment after a
preprocessor directive contains any non-ascii characters.

Bug: 940865
Change-Id: I57fb201ec88d73093776c7d200d62cc9e7ce2b41
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1846073Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Cr-Commit-Position: refs/heads/master@{#703856}

third_party/blink/renderer/modules/webgl/webgl_rendering_context_base.cc

@@ -445,6 +445,7 @@ void StripComments::Process(UChar c) {
       break;
 
     case kMiddleOfLine:
+    case kInPreprocessorDirective:
       if (c == '/' && Peek(temp)) {
         if (temp == '/') {
           parse_state_ = kInSingleLineComment;
@@ -468,14 +469,6 @@ void StripComments::Process(UChar c) {
       Emit(c);
       break;
 
-    case kInPreprocessorDirective:
-      // No matter what the character is, just pass it
-      // through. Do not parse comments in this state. This
-      // might not be the right thing to do long term, but it
-      // should handle the #error preprocessor directive.
-      Emit(c);
-      break;
-
     case kInSingleLineComment:
       // Line-continuation characters are processed before comment processing.
       // Advance string if a new line character is immediately behind