[Chromecast] Depend on Chromium's freetype-android

This change helps to reduce the external dependencies for OEMs to support cast_shell.

Updates third_party/libpng so it can be used as a dependency for freetype on Chromecast.

Remove the gyp variable use_custom_freetype because it is now unused.

BUG=internal b/26249831
TEST=builds and runs with gyp and gn

Review URL: https://codereview.chromium.org/1627533002

Cr-Original-Commit-Position: refs/heads/master@{#372996}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0ddf78a46654c13f9ee7de921a820087f45375e3

common.gypi

@@ -1885,7 +1885,6 @@
         'use_system_fontconfig%': 1,
       }],
       ['chromecast==1', {
-        'use_custom_freetype%': 0,
         'use_playready%': 0,
         'conditions': [
           ['target_arch=="arm"', {

config/linux/BUILD.gn

@@ -34,6 +34,8 @@ config("fontconfig") {
 }
 
 pkg_config("freetype2") {
+  visibility = [ "//build/linux:freetype2" ]
+
   packages = [ "freetype2" ]
 }
 

linux/BUILD.gn

@@ -11,8 +11,6 @@ gypi_values = exec_script("//build/gypi_to_gn.py",
                           "scope",
                           [ "system.gyp" ])
 
-use_system_fontconfig = !is_chromecast
-
 # If brlapi isn't needed, don't require it to be installed.
 if (use_brlapi) {
   config("brlapi_config") {
@@ -107,11 +105,24 @@ group("udev") {
 }
 
 group("fontconfig") {
-  if (use_system_fontconfig) {
-    public_configs = [ "//build/config/linux:fontconfig" ]
-  } else {
+  if (is_chromecast) {
+    # Chromecast platform does not provide fontconfig
     public_deps = [
       "//third_party/fontconfig",
     ]
+  } else {
+    public_configs = [ "//build/config/linux:fontconfig" ]
+  }
+}
+
+group("freetype2") {
+  if (is_chromecast) {
+    # Chromecast platform doesn't provide freetype, so use Chromium's.
+    # The version in freetype-android is unmodified from freetype2 upstream.
+    public_deps = [
+      "//third_party/freetype-android:freetype",
+    ]
+  } else {
+    public_configs = [ "//build/config/linux:freetype2" ]
   }
 }

linux/system.gyp

@@ -780,7 +780,14 @@
       'target_name': 'freetype2',
       'type': 'none',
       'conditions': [
-        ['_toolset=="target"', {
+        ['chromecast==1', {
+          'dependencies': [
+            '../../third_party/freetype-android/freetype.gyp:ft2',
+          ],
+          'export_dependent_settings' : [
+            '../../third_party/freetype-android/freetype.gyp:ft2',
+          ],
+        }, '_toolset=="target"', {
           'direct_dependent_settings': {
             'cflags': [
               '<!@(<(pkg-config) --cflags freetype2)',