Fixing remaining VC++ 2015 64-bit build breaks

content/common/sandbox_win.cc

Index: content/common/sandbox_win.cc
diff --git a/content/common/sandbox_win.cc b/content/common/sandbox_win.cc
index 88f703cef3388f99df46ec9f4a951c33c4793fc1..d9b031e36804758abbaa4dcdc39c349d8f800f68 100644
--- a/content/common/sandbox_win.cc
+++ b/content/common/sandbox_win.cc
@@ -747,8 +747,12 @@ base::Process StartSandboxedProcess(
       if (direct_write_font_cache_section.Open(name, true)) {
         void* shared_handle = policy->AddHandleToShare(
             direct_write_font_cache_section.handle().GetHandle());
-        cmd_line->AppendSwitchASCII(switches::kFontCacheSharedHandle,
-            base::UintToString(reinterpret_cast<unsigned int>(shared_handle)));
+        // Cast through uintptr_t and then unsigned int to make the truncation
+        // explicit. Handles are size-of-pointer but are always 32-bit values.
+        cmd_line->AppendSwitchASCII(
+            switches::kFontCacheSharedHandle,
+            base::UintToString(static_cast<unsigned int>(
+                reinterpret_cast<uintptr_t>(shared_handle))));
       }
     }
   }