Revert "Don't export ANGLE platform methods."

This reverts commit 7a11f4415e.

Reason for revert:
Running Android games using ANGLE results in crashes or hangs.

Original change's description:
> Don't export ANGLE platform methods.
>
> These functions are loaded through eglGetProcAddress. We don't need
> to export these extra symbols and increase our binary size.
>
> Bug: chromium:1445969
> Change-Id: I494bbcb86973f167e8245b56e6eb73da7eab69f5
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4538367
> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>

Bug: b/283233503
Change-Id: I42418c0dabc440fb13ce3d48d63b2622b9edd15e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4544216
Commit-Queue: Mark Łobodziński <mark@lunarg.com>
Reviewed-by: Mark Łobodziński <mark@lunarg.com>
Reviewed-by: Yuxin Hu <yuxinhu@google.com>

include/platform/PlatformMethods.h

@@ -313,15 +313,15 @@ extern "C" {
 // The application should set any platform methods it cares about on the returned pointer.
 // If display is not valid, behaviour is undefined.
 
-bool ANGLE_APIENTRY ANGLEGetDisplayPlatform(angle::EGLDisplayType display,
-                                            const char *const methodNames[],
-                                            unsigned int methodNameCount,
-                                            void *context,
-                                            void *platformMethodsOut);
+ANGLE_PLATFORM_EXPORT bool ANGLE_APIENTRY ANGLEGetDisplayPlatform(angle::EGLDisplayType display,
+                                                                  const char *const methodNames[],
+                                                                  unsigned int methodNameCount,
+                                                                  void *context,
+                                                                  void *platformMethodsOut);
 
 // Sets the platform methods back to their defaults.
 // If display is not valid, behaviour is undefined.
-void ANGLE_APIENTRY ANGLEResetDisplayPlatform(angle::EGLDisplayType display);
+ANGLE_PLATFORM_EXPORT void ANGLE_APIENTRY ANGLEResetDisplayPlatform(angle::EGLDisplayType display);
 }  // extern "C"
 
 namespace angle