win: Work towards getting 'minidump' to compile

minidump/minidump_context_writer.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 142 matching lines @@
     const CPUContextX86_64* context_snapshot) {
   DCHECK_EQ(state(), kStateMutable);
   DCHECK_EQ(context_.context_flags, kMinidumpContextAMD64);
 
   context_.context_flags = kMinidumpContextAMD64All;
 
   context_.mx_csr = context_snapshot->fxsave.mxcsr;
   context_.cs = context_snapshot->cs;
   context_.fs = context_snapshot->fs;
   context_.gs = context_snapshot->gs;
-  context_.eflags = context_snapshot->rflags;
+  // The top 32 bits of rflags are reserved/unused.
+  context_.eflags = static_cast<uint32_t>(context_snapshot->rflags);
   context_.dr0 = context_snapshot->dr0;
   context_.dr1 = context_snapshot->dr1;
   context_.dr2 = context_snapshot->dr2;
   context_.dr3 = context_snapshot->dr3;
   context_.dr6 = context_snapshot->dr6;
   context_.dr7 = context_snapshot->dr7;
   context_.rax = context_snapshot->rax;
   context_.rcx = context_snapshot->rcx;
   context_.rdx = context_snapshot->rdx;
   context_.rbx = context_snapshot->rbx;
@@ skipping 28 matching lines @@
   return file_writer->Write(&context_, sizeof(context_));
 }
 
 size_t MinidumpContextAMD64Writer::ContextSize() const {
   DCHECK_GE(state(), kStateFrozen);
 
   return sizeof(context_);
 }
 
 }  // namespace crashpad