Add memory pressure listener to Blob storage

storage/common/blob_storage/blob_storage_constants.h

Index: storage/common/blob_storage/blob_storage_constants.h
diff --git a/storage/common/blob_storage/blob_storage_constants.h b/storage/common/blob_storage/blob_storage_constants.h
index f51b012bc07c7b9570688eb9d516b4dd557b4516..ec354bc0d343b12d9af4af5a7f651f9f6bf7db38 100644
--- a/storage/common/blob_storage/blob_storage_constants.h
+++ b/storage/common/blob_storage/blob_storage_constants.h
@@ -23,8 +23,10 @@ constexpr uint64_t kDefaultMaxPageFileSize = 100ull * 1024 * 1024;
 #if defined(OS_ANDROID)
 // On minimal Android maximum in-memory space can be as low as 5MB.
 constexpr uint64_t kDefaultMinPageFileSize = 5ull * 1024 * 1024 / 2;
+constexpr uint64_t kDefaultMinPageFileSizeUnderPressure = 100 * 1024;
 #else
 constexpr uint64_t kDefaultMinPageFileSize = 5ull * 1024 * 1024;
+constexpr uint64_t kDefaultMinPageFileSizeUnderPressure = 1ull * 1024 * 1024;
 #endif
 
 // All sizes are in bytes.
@@ -61,6 +63,10 @@ struct STORAGE_COMMON_EXPORT BlobStorageLimits {
   // This is the minimum file size we can use when paging blob items to disk.
   // We combine items until we reach at least this size.
   uint64_t min_page_file_size = kDefaultMinPageFileSize;
+  // Minimum page file size to use when under memory pressure (to avoid causing
+  // peaks due to file write buffers).
+  uint64_t min_page_file_size_under_pressure =
+      kDefaultMinPageFileSizeUnderPressure;
   // This is the maximum file size we can create.
   uint64_t max_file_size = kDefaultMaxPageFileSize;
 };