SkPDF:  Move SkFlate into src/pdf (part 1/3) [reland]

Rename to SkDeflate so Chromium builders continue to work

Next, we change remove SkFlate from Chromium build files, then we can delete SkFlate.

Review URL: https://codereview.chromium.org/1285913002
diff --git a/tests/PDFPrimitivesTest.cpp b/tests/PDFPrimitivesTest.cpp
index 013d586..b0b7765 100644
--- a/tests/PDFPrimitivesTest.cpp
+++ b/tests/PDFPrimitivesTest.cpp
@@ -9,7 +9,7 @@
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkDocument.h"
-#include "SkFlate.h"
+#include "SkDeflate.h"
 #include "SkImageEncoder.h"
 #include "SkMatrix.h"
 #include "SkPDFCanon.h"