Wrap all preprocessor code in the angle namespace.

BUG=836820
BUG=801364

Change-Id: I08b6a2f9f12b689e09df6efd916c313e71e8a051
Reviewed-on: https://chromium-review.googlesource.com/1028581
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
diff --git a/src/compiler/preprocessor/ExpressionParser.h b/src/compiler/preprocessor/ExpressionParser.h
index 0f2901b..c5cd7f7 100644
--- a/src/compiler/preprocessor/ExpressionParser.h
+++ b/src/compiler/preprocessor/ExpressionParser.h
@@ -10,6 +10,9 @@
 #include "common/angleutils.h"
 #include "compiler/preprocessor/DiagnosticsBase.h"
 
+namespace angle
+{
+
 namespace pp
 {
 
@@ -40,4 +43,6 @@
 
 }  // namespace pp
 
+}  // namespace angle
+
 #endif  // COMPILER_PREPROCESSOR_EXPRESSIONPARSER_H_