Set discardable shared memory limit to 64MB on Chromecast devices.

Bug: 876359
Change-Id: I554cdd9a7124312da670e6d1878b0bcddb2d74f5
Reviewed-on: https://chromium-review.googlesource.com/1183887
Commit-Queue: Jason Roberts <jasonroberts@chromium.org>
Reviewed-by: Peng Huang <penghuang@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585169}

components/discardable_memory/service/discardable_shared_memory_manager.cc

@@ -152,6 +152,12 @@ class DiscardableMemoryImpl : public base::DiscardableMemory {
 int64_t GetDefaultMemoryLimit() {
   const int kMegabyte = 1024 * 1024;
 
+#if defined(CHROMECAST_BUILD)
+  // Bypass IsLowEndDevice() check and fix max_default_memory_limit to 64MB on
+  // Chromecast devices. Set value here as IsLowEndDevice() is used on some, but
+  // not all Chromecast devices.
+  int64_t max_default_memory_limit = 64 * kMegabyte;
+#else
 #if defined(OS_ANDROID)
   // Limits the number of FDs used to 32, assuming a 4MB allocation size.
   int64_t max_default_memory_limit = 128 * kMegabyte;
@@ -162,6 +168,7 @@ int64_t GetDefaultMemoryLimit() {
   // Use 1/8th of discardable memory on low-end devices.
   if (base::SysInfo::IsLowEndDevice())
     max_default_memory_limit /= 8;
+#endif
 
 #if defined(OS_LINUX)
   base::FilePath shmem_dir;