Move non-linux specific code from base/linux_util to app/gtk_util...

app/gtk_util.cc

Index: app/gtk_util.cc
===================================================================
--- app/gtk_util.cc	(revision 46986)
+++ app/gtk_util.cc	(working copy)
@@ -31,6 +31,26 @@
   GetWidgetSizeFromCharacters(widget, chars, lines, width, height);
 }
 
+uint8_t* BGRAToRGBA(const uint8_t* pixels, int width, int height, int stride) {
+  if (stride == 0)
+    stride = width * 4;
+
+  uint8_t* new_pixels = static_cast<uint8_t*>(malloc(height * stride));
+
+  // We have to copy the pixels and swap from BGRA to RGBA.
+  for (int i = 0; i < height; ++i) {
+    for (int j = 0; j < width; ++j) {
+      int idx = i * stride + j * 4;
+      new_pixels[idx] = pixels[idx + 2];
+      new_pixels[idx + 1] = pixels[idx + 1];
+      new_pixels[idx + 2] = pixels[idx];
+      new_pixels[idx + 3] = pixels[idx + 3];
+    }
+  }
+
+  return new_pixels;
+}
+
 void GetWidgetSizeFromCharacters(
     GtkWidget* widget, double width_chars, double height_lines,
     int* width, int* height) {