Port "Eclipse CDT settings" file generation from GYP to GN

tools/gn/command_gen.cc

Index: tools/gn/command_gen.cc
diff --git a/tools/gn/command_gen.cc b/tools/gn/command_gen.cc
index b4faaa59a5e5710f2b6fdc4fcb8a58134ca7c6a1..ddef60440b319d9fb5872018c09576d4603c6e19 100644
--- a/tools/gn/command_gen.cc
+++ b/tools/gn/command_gen.cc
@@ -10,6 +10,7 @@
 #include "base/timer/elapsed_timer.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/commands.h"
+#include "tools/gn/eclipse_writer.h"
 #include "tools/gn/ninja_target_writer.h"
 #include "tools/gn/ninja_writer.h"
 #include "tools/gn/runtime_deps.h"
@@ -26,6 +27,7 @@ namespace {
 
 const char kSwitchCheck[] = "check";
 const char kSwitchIde[] = "ide";
+const char kSwitchIdeValueEclipse[] = "eclipse";
 const char kSwitchIdeValueVs[] = "vs";
 
 // Called on worker thread to write the ninja file.
@@ -151,8 +153,16 @@ bool RunIdeWriter(const std::string& ide,
                   const BuildSettings* build_settings,
                   Builder* builder,
                   Err* err) {
-  if (ide == kSwitchIdeValueVs) {
-    base::ElapsedTimer timer;
+  base::ElapsedTimer timer;
+  if (ide == kSwitchIdeValueEclipse) {
+    bool res = EclipseWriter::RunAndWriteFile(build_settings, builder, err);
+    if (res) {
+      OutputString("Generating Eclipse settings took " +
+                   base::Int64ToString(timer.Elapsed().InMilliseconds()) +
+                   "ms\n");
+    }
+    return res;
+  } else if (ide == kSwitchIdeValueVs) {
     bool res =
         VisualStudioWriter::RunAndWriteFiles(build_settings, builder, err);
     if (res &&
@@ -189,6 +199,18 @@ const char kGen_Help[] =
     "  --ide=<ide_name>\n"
     "    Also generate files for an IDE. Currently supported values:\n"
     "      'vs' - Visual Studio project/solution files.\n"
+    "      'eclipse' - Eclipse CDT settings file.\n"
+    "\n"
+    "  Eclipse IDE Support\n"

[brettw, 2016/02/17 20:59:09]

For this, can you put this below the "See \"gn help..." comment and format like
so:

  "  See \"gn help switches\" for the common command-line switches.\n"
  "\n"
  "Eclipse IDE Support\n"
  "\n"
  "  GN does not...\n"

Putting the Eclipse heading not indented will trigger heading syntax
highlighting and make the help look prettier, and I think it makes sense to put
this big block outside of the section on switches.

+    "    GN DOES NOT generate Eclipse CDT projects. Instead, it generates a\n"
+    "    settings file which can be imported into an Eclipse CDT project. The\n"
+    "    XML file contains a list of include paths and defines. Because GN\n"
+    "    does not generate a full .cproject definition, it is not possible to\n"
+    "    properly define includes/defines for each file individually.\n"
+    "    Instead, one set of includes/defines is generated for the entire\n"
+    "    project. This works fairly well (and is a vast improvement in\n"
+    "    in general), but may still result in a few indexer issues here and\n"
+    "    there.\n"
     "\n"
     "  See \"gn help switches\" for the common command-line switches.\n";