GN: Update heap stubs for android

Source/platform/BUILD.gn

Index: Source/platform/BUILD.gn
diff --git a/Source/platform/BUILD.gn b/Source/platform/BUILD.gn
index e80d157d9554da818315b10e3de8884ce53a6c00..cea25c0f751c932da6d9cdaeabe3c1edbcca77b5 100644
--- a/Source/platform/BUILD.gn
+++ b/Source/platform/BUILD.gn
@@ -7,7 +7,6 @@ import("//third_party/WebKit/Source/build/scripts/scripts.gni")
 import("//third_party/WebKit/Source/config.gni")
 import("//third_party/WebKit/Source/platform/platform.gni")
 import("//third_party/WebKit/Source/platform/platform_generated.gni")
-import("//third_party/yasm/yasm_assemble.gni")
 
 # Most targets in this file are private actions so use that as the default.
 visibility = ":*"
@@ -334,16 +333,13 @@ component("platform") {
   }
 }
 
+if (cpu_arch == "x86" || cpu_arch == "x64") {
+import("//third_party/yasm/yasm_assemble.gni")
+
 yasm_assemble("heap_asm_stubs") {
-  if (cpu_arch == "x86" || cpu_arch == "x64") {
-    sources = [ "heap/asm/SaveRegisters_x86.asm" ]
-  } else if (cpu_arch == "arm") {
-    sources = [ "heap/asm/SaveRegisters_arm.S" ]
-  } else if (cpu_arch == "arm64") {
-    sources = [ "heap/asm/SaveRegisters_arm64.S" ]
-  } else if (cpu_arch == "mipsel") {
-    sources = [ "heap/asm/SaveRegisters_mips.S" ]
-  }
+  assert(cpu_arch == "x86" || cpu_arch == "x64")
+
+  sources = [ "heap/asm/SaveRegisters_x86.asm" ]
 
   yasm_flags = []
   if (is_mac) {
@@ -357,13 +353,30 @@ yasm_assemble("heap_asm_stubs") {
     } else {
       yasm_flags += [ "-DX64POSIX=1" ]
     }
-  } else if (cpu_arch == "x86") {
+  } else {  # cpu_arch == "x86"
     yasm_flags += [ "-DIA32=1" ]
-  } else if (cpu_arch == "arm") {
-    yasm_flags += [ "-DARM=1" ]
   }
 }
 
+} else { # cpu_arch == "x86" || cpu_arch == "x64"
+
+source_set("heap_asm_stubs") {
+  if (cpu_arch == "arm") {
+    sources = [ "heap/asm/SaveRegisters_arm.S" ]
+  } else if (cpu_arch == "arm64") {
+    sources = [ "heap/asm/SaveRegisters_arm64.S" ]
+  } else if (cpu_arch == "mipsel") {
+    sources = [ "heap/asm/SaveRegisters_mips.S" ]
+  }
+
+  if (cpu_arch == "arm") {
+    defines = [ "ARM=1" ]
+  }
+
+}
+
+} # cpu_arch == "x86" || cpu_arch == "x64"
+
 
 test("heap_unittests") {
   visibility = "//third_party/WebKit/*"