Fix GN build for libEGL.

Our build in GN differed slightly from our gyp build, causing the
linker to complain about inconsistent linkage. Also remove some
stray definitions of EGLAPI from our headers.

Change-Id: I5d3a09ccb0cec528ead33944ce0996cceed32d86
Reviewed-on: https://chromium-review.googlesource.com/210821
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 98bd164..396d7d3 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -199,6 +199,12 @@
   shared_library("libEGL") {
     sources = rebase_path(egl_gypi.angle_libegl_sources, ".", "src")
 
+    defines = [
+      "GL_APICALL=",
+      "GL_GLEXT_PROTOTYPES=",
+      "EGLAPI=",
+    ]
+
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [
       ":internal_config",
@@ -206,7 +212,7 @@
     ]
 
     if (is_debug) {
-      defines = [ "ANGLE_ENABLE_PERF" ]
+      defines += [ "ANGLE_ENABLE_PERF" ]
     }
 
     include_dirs = [ "src/libGLESv2" ]
diff --git a/src/libEGL/Config.h b/src/libEGL/Config.h
index 680337b..9844114 100644
--- a/src/libEGL/Config.h
+++ b/src/libEGL/Config.h
@@ -11,7 +11,6 @@
 #ifndef INCLUDE_CONFIG_H_
 #define INCLUDE_CONFIG_H_
 
-#define EGLAPI
 #include <EGL/egl.h>
 
 #include <set>
diff --git a/src/libEGL/Surface.h b/src/libEGL/Surface.h
index 2361fcd..24c66b7 100644
--- a/src/libEGL/Surface.h
+++ b/src/libEGL/Surface.h
@@ -11,7 +11,6 @@
 #ifndef LIBEGL_SURFACE_H_
 #define LIBEGL_SURFACE_H_
 
-#define EGLAPI
 #include <EGL/egl.h>
 
 #include "common/angleutils.h"
@@ -105,7 +104,7 @@
     EGLint mSwapInterval;
     EGLint mPostSubBufferSupported;
     EGLint mFixedSize;
-    
+
     bool mSwapIntervalDirty;
     gl::Texture2D *mTexture;
 };
diff --git a/src/libEGL/main.h b/src/libEGL/main.h
index 77da8f0..07f5b9e 100644
--- a/src/libEGL/main.h
+++ b/src/libEGL/main.h
@@ -9,7 +9,6 @@
 #ifndef LIBEGL_MAIN_H_
 #define LIBEGL_MAIN_H_
 
-#define EGLAPI
 #include <EGL/egl.h>
 #include <EGL/eglext.h>