Initial gtk3 support

build/linux/system.gyp

Index: build/linux/system.gyp
diff --git a/build/linux/system.gyp b/build/linux/system.gyp
index ab20951b9c91c6f08c1a750c6ec26f0a4f1699c3..6b6ed6310b3c6bfa064efb571f7d5188da7df0c9 100644
--- a/build/linux/system.gyp
+++ b/build/linux/system.gyp
@@ -113,15 +113,15 @@
             ['_toolset=="target"', {
               'direct_dependent_settings': {
                 'cflags': [
-                  '<!@(<(pkg-config) --cflags gdk-2.0)',
+                  '<!@(<(pkg-config) --cflags gdk-3.0)',
                 ],
               },
               'link_settings': {
                 'ldflags': [
-                  '<!@(<(pkg-config) --libs-only-L --libs-only-other gdk-2.0)',
+                  '<!@(<(pkg-config) --libs-only-L --libs-only-other gdk-3.0)',
                 ],
                 'libraries': [
-                  '<!@(<(pkg-config) --libs-only-l gdk-2.0)',
+                  '<!@(<(pkg-config) --libs-only-l gdk-3.0)',
                 ],
               },
             }],
@@ -134,7 +134,7 @@
           'variables': {
             # gtk requires gmodule, but it does not list it as a dependency
             # in some misconfigured systems.
-            'gtk_packages': 'gmodule-2.0 gtk+-2.0 gthread-2.0',
+            'gtk_packages': 'gmodule-2.0 gtk+-3.0 gthread-2.0',
           },
           'conditions': [
             ['_toolset=="target"', {
@@ -175,15 +175,15 @@
             ['_toolset=="target"', {
               'direct_dependent_settings': {
                 'cflags': [
-                  '<!@(<(pkg-config) --cflags gtk+-unix-print-2.0)',
+                  '<!@(<(pkg-config) --cflags gtk+-unix-print-3.0)',
                 ],
               },
               'link_settings': {
                 'ldflags': [
-                  '<!@(<(pkg-config) --libs-only-L --libs-only-other gtk+-unix-print-2.0)',
+                  '<!@(<(pkg-config) --libs-only-L --libs-only-other gtk+-unix-print-3.0)',
                 ],
                 'libraries': [
-                  '<!@(<(pkg-config) --libs-only-l gtk+-unix-print-2.0)',
+                  '<!@(<(pkg-config) --libs-only-l gtk+-unix-print-3.0)',
                 ],
               },
             }],