Revert "PR_SET_DUMPABLE 1 briefly if opening pagemap fails"

This reverts commit c63cb6f2.

Reason for revert: crbug.com/1130358

Original change's description:
> PR_SET_DUMPABLE 1 briefly if opening pagemap fails
> 
> This is often necessary on Android to read /proc/self/pagemap. Without
> prctl(PR_SET_DUMPABLE) opening this file fails in 94% of cases on
> Canary. This potentially leads to bias in reporting
> MappedAndResidentMemoryFootprint2.
> 
> Bug: 1070618
> Change-Id: Ic7f965099c4b3ba822baf248eb80d33678996188
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2416377
> Commit-Queue: Egor Pasko <pasko@chromium.org>
> Reviewed-by: Robert Sesek <rsesek@chromium.org>
> Reviewed-by: ssid <ssid@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#808298}

TBR=pasko@chromium.org,ssid@chromium.org,rsesek@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1070618
Change-Id: Icae38145675e215c8ba1b685308d63b0a60b1d28
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2420776Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808758}

services/resource_coordinator/public/cpp/memory_instrumentation/os_metrics_linux.cc

@@ -5,8 +5,6 @@
 #include <dlfcn.h>
 #include <fcntl.h>
 #include <stdint.h>
-#include <sys/prctl.h>
-
 #include <memory>
 
 #include "base/android/library_loader/anchor_functions.h"
@@ -230,39 +228,6 @@ uint32_t ReadLinuxProcSmapsFile(FILE* smaps_file,
   return num_valid_regions;
 }
 
-// RAII class making the current process dumpable via prctl(PR_SET_DUMPABLE, 1),
-// in case it is not currently dumpable as described in proc(5) and prctl(2).
-// Noop if the original dumpable state could not be determined.
-class ScopedProcessSetDumpable {
- public:
-  ScopedProcessSetDumpable() {
-    int result = prctl(PR_GET_DUMPABLE, 0, 0, 0, 0);
-    if (result < 0) {
-      PLOG(ERROR) << "prctl";
-      was_dumpable_ = true;  // Avoids prctl on destruction.
-      return;
-    }
-    was_dumpable_ = result > 0;
-
-    if (!was_dumpable_) {
-      result = prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
-      PLOG_IF(ERROR, result != 0) << "prctl";
-    }
-  }
-
-  ScopedProcessSetDumpable(const ScopedProcessSetDumpable&) = delete;
-  ScopedProcessSetDumpable& operator=(const ScopedProcessSetDumpable&) = delete;
-
-  ~ScopedProcessSetDumpable() {
-    if (!was_dumpable_) {
-      PCHECK(prctl(PR_SET_DUMPABLE, 0, 0, 0, 0));
-    }
-  }
-
- private:
-  bool was_dumpable_;
-};
-
 }  // namespace
 
 FILE* g_proc_smaps_for_testing = nullptr;
@@ -363,14 +328,8 @@ OSMetrics::MappedAndResidentPagesDumpState OSMetrics::GetMappedAndResidentPages(
 
   base::ScopedFILE pagemap_file(fopen(kPagemap, "r"));
   if (!pagemap_file.get()) {
-    {
-      ScopedProcessSetDumpable set_dumpable;
-      pagemap_file.reset(fopen(kPagemap, "r"));
-    }
-    if (!pagemap_file.get()) {
-      DLOG(WARNING) << "Could not open " << kPagemap;
-      return OSMetrics::MappedAndResidentPagesDumpState::kAccessPagemapDenied;
-    }
+    DLOG(WARNING) << "Could not open " << kPagemap;
+    return OSMetrics::MappedAndResidentPagesDumpState::kAccessPagemapDenied;
   }
 
   const size_t kPageSize = base::GetPageSize();