Update default VS to 2019

Visual Studio 2019 is stable, widely used, and has a much
better debugging experience than VS2017. Switch to using
that as the default when `--ide=vs` is passed to `gn gen`.

Bug: chromium:1038361
Change-Id: I4dd9ab3316d71e9f8ec08050f8a60c7556d3018d
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/6900
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Brett Wilson <brettw@chromium.org>

docs/reference.md

diff --git a/docs/reference.md b/docs/reference.md
index e574657..90cc029 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -693,7 +693,7 @@
       Generate files for an IDE. Currently supported values:
       "eclipse" - Eclipse CDT settings file.
       "vs" - Visual Studio project/solution files.
-             (default Visual Studio version: 2017)
+             (default Visual Studio version: 2019)
       "vs2013" - Visual Studio 2013 project/solution files.
       "vs2015" - Visual Studio 2015 project/solution files.
       "vs2017" - Visual Studio 2017 project/solution files.

src/gn/command_gen.cc

diff --git a/src/gn/command_gen.cc b/src/gn/command_gen.cc
index 84f6e20..bae2e4b 100644
--- a/src/gn/command_gen.cc
+++ b/src/gn/command_gen.cc
@@ -202,13 +202,13 @@
   } else if (ide == kSwitchIdeValueVs || ide == kSwitchIdeValueVs2013 ||
              ide == kSwitchIdeValueVs2015 || ide == kSwitchIdeValueVs2017 ||
              ide == kSwitchIdeValueVs2019) {
-    VisualStudioWriter::Version version = VisualStudioWriter::Version::Vs2017;
+    VisualStudioWriter::Version version = VisualStudioWriter::Version::Vs2019;
     if (ide == kSwitchIdeValueVs2013)
       version = VisualStudioWriter::Version::Vs2013;
     else if (ide == kSwitchIdeValueVs2015)
       version = VisualStudioWriter::Version::Vs2015;
-    else if (ide == kSwitchIdeValueVs2019)
-      version = VisualStudioWriter::Version::Vs2019;
+    else if (ide == kSwitchIdeValueVs2017)
+      version = VisualStudioWriter::Version::Vs2017;
 
     std::string sln_name;
     if (command_line->HasSwitch(kSwitchSln))
@@ -334,7 +334,7 @@
       Generate files for an IDE. Currently supported values:
       "eclipse" - Eclipse CDT settings file.
       "vs" - Visual Studio project/solution files.
-             (default Visual Studio version: 2017)
+             (default Visual Studio version: 2019)
       "vs2013" - Visual Studio 2013 project/solution files.
       "vs2015" - Visual Studio 2015 project/solution files.
       "vs2017" - Visual Studio 2017 project/solution files.