documentation: SkDocument::MakePDF()

also, update some tools.

DOCS_PREVIEW= https://skia.org/user/sample/pdf?cl=1936283003
DOCS_PREVIEW= https://skia.org/user/api/canvas?cl=1936283003

Review-Url: https://codereview.chromium.org/1936283003
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index ba2e6cc..6500612 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -1379,7 +1379,7 @@
 #ifdef SK_BUILD_FOR_ANDROID
         name.prepend("/sdcard/");
 #endif
-        fPDFDocument.reset(SkDocument::CreatePDF(name.c_str()));
+        fPDFDocument = SkDocument::MakePDF(name.c_str());
         canvas = fPDFDocument->beginPage(this->width(), this->height());
     } else if (fSaveToSKP) {
         canvas = fRecorder.beginRecording(9999, 9999, nullptr, 0);