Shove the tests into a different file

Also add descriptions because those are nice

Change-Id: I2d0480acf17af2700c8b7fb7228203e16a068f6b
diff --git a/libs/hwui/tests/TestContext.h b/libs/hwui/tests/TestContext.h
index 7b30fc1..2bbe5df 100644
--- a/libs/hwui/tests/TestContext.h
+++ b/libs/hwui/tests/TestContext.h
@@ -32,6 +32,8 @@
 extern DisplayInfo gDisplay;
 #define dp(x) ((x) * android::uirenderer::test::gDisplay.density)
 
+DisplayInfo getBuiltInDisplay();
+
 class TestContext {
 public:
     TestContext();