Revert "SkStream: remove some WStream functions from public api"

This reverts commit 8b681105077393ce8fb5bef0c1b55461ac2a5792.

Reason for revert: breaks bots

Original change's description:
> SkStream: remove some WStream functions from public api
> 
> move functions to SkStringPriv.h
> 
> also add SkStrAppendU32Hex() function, and re-write
> SkString::insertHex() to use SkStrAppendU32Hex.
> 
> add unit tests.
> 
> Change-Id: Ieda98fb4106db71565b607e593713a91a5ddd892
> Reviewed-on: https://skia-review.googlesource.com/151986
> Reviewed-by: Cary Clark <caryclark@google.com>
> Commit-Queue: Hal Canary <halcanary@google.com>

TBR=halcanary@google.com,bungeman@google.com,caryclark@google.com,reed@google.com

Change-Id: Idbac615092f46c18b38e08385dafba20930f0ff0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/152121
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index 541ca77..f321284 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -41,7 +41,6 @@
 #include "SkRasterClip.h"
 #include "SkScopeExit.h"
 #include "SkString.h"
-#include "SkStreamPriv.h"
 #include "SkSurface.h"
 #include "SkTemplates.h"
 #include "SkTextBlob.h"
@@ -437,7 +436,7 @@
             static_assert(SkPaint::kFill_Style == 0, "enum_must_match_value");
             static_assert(SkPaint::kStroke_Style == 1, "enum_must_match_value");
             static_assert(SkPaint::kStrokeAndFill_Style == 2, "enum_must_match_value");
-            SkWStreamWriteDecAsText(fContentStream, state.fTextFill);
+            fContentStream->writeDecAsText(state.fTextFill);
             fContentStream->writeText(" Tr\n");
             currentEntry()->fTextFill = state.fTextFill;
         }
@@ -1107,7 +1106,7 @@
     wStream->writeText("/");
     char prefix = SkPDFResourceDict::GetResourceTypePrefix(SkPDFResourceDict::kFont_ResourceType);
     wStream->write(&prefix, 1);
-    SkWStreamWriteDecAsText(wStream, fontIndex);
+    wStream->writeDecAsText(fontIndex);
     wStream->writeText(" ");
     SkPDFUtils::AppendScalar(textSize, wStream);
     wStream->writeText(" Tf\n");