add fsync to try to get complete skps from webpage picture capture

src/core/SkStream.cpp

Index: src/core/SkStream.cpp
diff --git a/src/core/SkStream.cpp b/src/core/SkStream.cpp
index fff8f3382209b9fd9509d55a916b711022d7721e..6795b97bdd5037c737c109d8b84238f26e0ed629 100644
--- a/src/core/SkStream.cpp
+++ b/src/core/SkStream.cpp
@@ -79,6 +79,10 @@ void SkWStream::flush()
 {
 }
 
+void SkWStream::sync()
+{
+}
+
 bool SkWStream::writeText(const char text[])
 {
     SkASSERT(text);
@@ -463,6 +467,13 @@ void SkFILEWStream::flush()
     }
 }
 
+void SkFILEWStream::sync()
+{
+    if (fFILE) {
+        sk_fsync(fFILE);
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////
 
 SkMemoryWStream::SkMemoryWStream(void* buffer, size_t size)