Set DISCARDABLE_MEMORY_ALWAYS_SUPPORTED_NATIVELY to true on Android.

build/common.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 400 matching lines @@
       # True if isolate should fail if the isolate files refer to files
       # that are missing.
       'test_isolation_fail_on_missing': 0,
 
       'sas_dll_path%': '<(DEPTH)/third_party/platformsdk_win7/files/redist/x86',
       'wix_path%': '<(DEPTH)/third_party/wix',
 
       # Managed users are enabled by default.
       'enable_managed_users%': 1,
 
+      # Set to true if platform natively supports discarable memory.

[jamesr, 2013/07/10 20:28:22]

typo "discarable" -> "discardable".

Saying "Set to true if ..." is redundant

[rmcilroy, 2013/07/11 08:57:27]

Done.

+      'native_discardable_memory%': 0,
+      # Set to true if platform sends memory pressure signals natively.

[jamesr, 2013/07/10 20:28:22]

blank line before this

[rmcilroy, 2013/07/11 08:57:27]

Done.

+      'native_memory_pressure_signals%': 0,
+
       'spdy_proxy_auth_origin%' : '',
       'spdy_proxy_auth_property%' : '',
       'spdy_proxy_auth_value%' : '',
 
       'conditions': [
         # A flag for POSIX platforms
         ['OS=="win"', {
           'os_posix%': 0,
         }, {
           'os_posix%': 1,
@@ skipping 75 matching lines @@
           'enable_automation%': 0,
           'enable_extensions%': 0,
           'enable_google_now%': 0,
           'enable_language_detection%': 1,
           'enable_printing%': 0,
           'enable_themes%': 0,
           'proprietary_codecs%': 1,
           'remoting%': 0,
           'arm_neon%': 0,
           'arm_neon_optional%': 1,
+          'native_discardable_memory%': 1,
+          'native_memory_pressure_signals%': 1,
         }],
 
         # Enable autofill dialog for Android and Views-enabled platforms for now.
         ['toolkit_views==1 or (OS=="android" and android_webview_build==0) or OS=="mac"', {
           'enable_autofill_dialog%': 1
         }],
 
         ['OS=="android" and android_webview_build==0', {
           'enable_webrtc%': 1,
         }],
@@ skipping 298 matching lines @@
     'gyp_managed_install%': 0,
     'create_standalone_apk%': 1,
     'google_tv%': '<(google_tv)',
     'enable_app_list%': '<(enable_app_list)',
     'use_default_render_theme%': '<(use_default_render_theme)',
     'enable_settings_app%': '<(enable_settings_app)',
     'google_api_key%': '<(google_api_key)',
     'google_default_client_id%': '<(google_default_client_id)',
     'google_default_client_secret%': '<(google_default_client_secret)',
     'enable_managed_users%': '<(enable_managed_users)',
+    'native_discardable_memory%': '<(native_discardable_memory)',
+    'native_memory_pressure_signals%': '<(native_memory_pressure_signals)',
     'spdy_proxy_auth_origin%': '<(spdy_proxy_auth_origin)',
     'spdy_proxy_auth_property%': '<(spdy_proxy_auth_property)',
     'spdy_proxy_auth_value%': '<(spdy_proxy_auth_value)',
 
     # Use system mesa instead of bundled one.
     'use_system_mesa%': 0,
 
     # Use system nspr instead of the bundled one.
     'use_system_nspr%': 0,
 
@@ skipping 2559 matching lines @@
           ['linux_use_gold_binary==1', {
             'ldflags': [
               # Put our gold binary in the search path for the linker.
               # We pass the path to gold to the compiler.  gyp leaves
               # unspecified what the cwd is when running the compiler,
               # so the normal gyp path-munging fails us.  This hack
               # gets the right path.
               '-B<(PRODUCT_DIR)/../../third_party/gold',
             ],
           }],
+          ['native_discardable_memory', {
+            'defines': ['DISCARDABLE_MEMORY_ALWAYS_SUPPORTED_NATIVELY'],
+          }],
+          ['native_memory_pressure_signals', {
+            'defines': ['SYSTEM_NATIVELY_SIGNALS_MEMORY_PRESSURE'],
+          }],
         ],
       },
     }],
     # FreeBSD-specific options; note that most FreeBSD options are set above,
     # with Linux.
     ['OS=="freebsd"', {
       'target_defaults': {
         'ldflags': [
           '-Wl,--no-keep-memory',
         ],
@@ skipping 1209 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }