Revert "sk_fgetsize to not use ftell."

This reverts commit eefa289a214ea3917e5e00554f231adb5ad6f712.

Reason for revert: Causing failures in BitmapFactoryTest. b/38233042

Original change's description:
> sk_fgetsize to not use ftell.
> 
> The previous version of sk_fgetsize used ftell and fseek to compute
> the size of a file. There are so many issues with this that it is called
> out by securecoding.cert.org as FIO19-C as a thing not to do. We already
> have correct code for computing the size of a file in the mmap code, so
> use that instead.
> 
> Change-Id: I1d771124989d0ec1523f6d858814ee563263213a
> Reviewed-on: https://skia-review.googlesource.com/9860
> Reviewed-by: Leon Scroggins <scroggo@google.com>
> Commit-Queue: Ben Wagner <bungeman@google.com>
> 

TBR=bungeman@google.com,scroggo@google.com
# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ie9392dde8747ae7c74ebfa00153705e316e841a2
Reviewed-on: https://skia-review.googlesource.com/17705
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/ports/SkOSFile_stdio.cpp b/src/ports/SkOSFile_stdio.cpp
index e79d87fc89..68c2d3d4d7 100644
--- a/src/ports/SkOSFile_stdio.cpp
+++ b/src/ports/SkOSFile_stdio.cpp
@@ -87,6 +87,24 @@ FILE* sk_fopen(const char path[], SkFILE_Flags flags) {
     return file;
 }
 
+size_t sk_fgetsize(FILE* f) {
+    SkASSERT(f);
+
+    long curr = ftell(f); // remember where we are
+    if (curr < 0) {
+        return 0;
+    }
+
+    fseek(f, 0, SEEK_END); // go to the end
+    long size = ftell(f); // record the size
+    if (size < 0) {
+        size = 0;
+    }
+
+    fseek(f, curr, SEEK_SET); // go back to our prev location
+    return size;
+}
+
 size_t sk_fwrite(const void* buffer, size_t byteCount, FILE* f) {
     SkASSERT(f);
     return fwrite(buffer, 1, byteCount, f);